Big Bang Theory Notes and Trivia

All notes and trivia from the hit show "Big Bang Theory"

S12E24 - The Stockholm Syndrome (Notes and Trivia)

Chuck Lorre had Ed Robertson record an acoustic version of the show's theme song to recreate the demo version that Robertson first recorded for Lorre before the show started.

During the final scene, Penny is wearing the same top she was wearing when she met Leonard and Sheldon for the first time in the Pilot (2007).

Howard's belt buckle in the scene when Sheldon and Amy have the meeting about what to do in Stockholm is the logo for The Big Bang Theory (2007).

In the final scene of the series, the group is eating in Leonard and Penny's living room. Their arrangement in their seats is exactly the same as the final shot of the group in the season 12 opening credits. Leonard also places his hand on the pregnant stomach of Penny and kisses her.

Nobody from the regular cast call their guest Sarah Michelle Gellar or any variation. Everyone who refers to her calls her Buffy the Vampire Slayer (1997).

Penny's maiden name was planned to be revealed when Sheldon calls out their names during his and Amy's acceptance speeches, but in fear of that moment upstaging the rest of the scene, it was decided at the last minute not to do so. Therefore, Penny's maiden name remains undisclosed.

The purpose of the large DNA model in Leonard and Sheldon's old room, which was already there before Leonard moved in, is finally revealed. When Sheldon explains to Leonard what he tried to invent with it, he says that it failed because the balls he used kept sticking to his pants. When he leaves with Amy a few moments later, a collection of balls can be seen stuck to the butt of his pants.

The title of the final episode (The Stockholm Syndrome (2019)) mirrors the feeling Sheldon had during the whole episode, complaining about his friends' (captors) flaws; until he finally accepted and started loving them when he read his final speech.

S12E23 - The Change Constant (Notes and Trivia)

The elevator in the apartment building, which has been broken since the pilot (because of a failed experiment by Leonard seen in flashback in The Staircase Implementation (2010)), is finally repaired.

This episode was broadcast back to back with The Stockholm Syndrome (2019) to serve as the first half of the series' finale. End credits and Chuck Lorre's Vanity Card were added for the home theatre versions.

This is the only episode that have the words to be continued at the end

Title reference: Sheldon has to be reminded that change is the only constant in his life.

S12E22 - The Maternal Conclusion (Notes and Trivia)

Title reference: Leonard and Beverly finally find closure for their difficult relationship. This is also the concluding episode for Leonard's mother on the show.

S12E21 - The Plagiarism Schism (Notes and Trivia)

A scene where Howard goes to the Cheesecake Factory with Raj to find the waitress who had a crush on him was shot, but was omitted from the episode. Mimi Gianopulos still gets credited for the deleted scene, though.

S12E20 - The Decision Reverberation (Notes and Trivia)

The new Avengers movie the gang is going to see is Avengers: Endgame (2019), which had been released three days before this episode's broadcast. Bernadette says that she wants to see the movie in 3D because she wants to feel close enough to lick Thor's abs; she would have been disappointed, because in the movie, Thor sported a large beer-belly.

S12E19 - The Inspiration Deprivation (Notes and Trivia)

Amy is told that she could be the fourth woman in history to win the Nobel Prize for Physics. This was true at the time of broadcast: in 2020, astronomer Andrea M. Ghez became the actual fourth female Physics winner for the discovery of a supermassive compact object at the center of the galaxy.

The number on the scooter "626-789-3495" belongs to "Footprints on the Moon" which is the name of the band that Raj and Howard formed. You could see it on their Facebook page.

This is the tenth and final time that "Soft Kitty" is sung on this show, and the first time since The Recollection Dissipation (2017). Due to a lawsuit with the estate of the song's original composer, the song was only rarely heard since season 8, but the lawsuit had since been dropped.

Title reference: Amy is devastated that her outburst may have cost her a Nobel Prize, thereby depriving women of the chance to be inspired to go into science, so to relax, she goes to a sensory deprivation tank.

S12E18 - The Laureate Accumulation (Notes and Trivia)

Title reference: the university is trying to get as many Nobel Prize laureates together in order to have them back up Sheldon and Amy in the race to the award.

S12E17 - The Conference Valuation (Notes and Trivia)

Melissa Rauch (Bernadette) and Ben Rauch (Darren, the guy who says "We get to go home?" to Penny) are brother and sister in real life.

The board game they are playing is Forbidden Island.

Title reference: Penny learns her personal and commercial worth during a conference.

S12E16 - The D&D Vortex (Notes and Trivia)

At Wil Wheaton's house, there's a poster of the movie Stand by Me (1986), in which he starred.

In an interview with People magazine, Joe Manganiello said that during the Covid-19 quarantine he actually did play D and D. He also revealed on his Instagram page that the dice he uses in the D&D game belonged to the creator of the game E. Gary Gygax. The dice were given to Manganiello by Gygax's son.

Title reference: A secret celebrity Dungeons & Dragons games causes a whirlwind of actions by the gang to get in.

S12E15 - The Donation Oscillation (Notes and Trivia)

Final appearance of Penny's ex-boyfriend Zack Johnson (Brian Thomas Smith).

The last episode to feature Keith Carradine as Penny's dad, Wyatt.

The name of Penny's sister Lisa is finally revealed, although she never appeared on screen.

The reference Sheldon made to the Underdog balloon getting away at Macy's parade was also used as part of a comedy sketch in the first season of Friends (1994).

S12E14 - The Meteorite Manifestation (Notes and Trivia)

In this context, kerf is a term used for the width of a saw blade. So "kerf loss" would be speaking to the amount that would be lost to the width of the blade.

Leonard is finally using the laser he bought for himself with university funding in The Grant Allocation Derivation (2018).

Title reference: the gang is preoccupied with one of Bert's meteorites, and speculate what horrors may come out when opened.

S12E13 - The Confirmation Polarization (Notes and Trivia)

Title reference: the confirmation of Amy and Sheldon's super-symmetry theory creates an uneasy situation between them with regards to who will receive credit or a Nobel Prize.

S12E12 - The Propagation Proposition (Notes and Trivia)

Near the end of the episode, when Penny is telling Leonard that she supports his decision, the front of the refrigerator is clearly visible behind Penny. Attached to the freezer door are two pictures of Leonard and Penny. One is of them in her apartment on her couch. The other appears to be a still image from The Nerdvana Annihilation (2008). It shows Leonard, without his glasses, holding Penny in the elevator shaft. Other items on the refrigerator include a periodic table, the apartment's official flag, post-it notes, a notepad, and multiple take-out menus.

Title reference: Zack asks Leonard to be a sperm donor so that he and his wife can "propagate" (reproduce).

S12E11 - The Paintball Scattering (Notes and Trivia)

Title reference: Tempers rise and people split apart during a heated paintball game.

S12E10 - The VCR Illumination (Notes and Trivia)

Second time Lance Barber has been on the show. The first time he played one of Leonard's old bullies in The Speckerman Recurrence (2011), and this time he plays Sheldon's dad, George Cooper Sr., whom he also plays in Young Sheldon (2017).

The Chuck Lorre vanity card (#604) for this episode is written in Russian. It translates to "guilty" in English.

The comic book Howard is reading on the couch is Mister Miracle #12, published on November 14, 2018 by DC Comics.

Title reference: Sheldon is inspired by an old speech that was taped on a VCR.

S12E09 - The Citation Negation (Notes and Trivia)

Howard's screen name on the video game he was playing is "Fr00tL00ps511", alluding to the unfortunate nickname he was given when he was in space.

The Vanity Card at the end shows a picture of the cast together with Stan Lee, who guest starred in The Excelsior Acquisition (2010), and died three days before the episode was broadcast.

S12E08 - The Consummation Deviation (Notes and Trivia)

Amy's dad Larry is in awe of Howard's magic tricks, which he can't do himself. Larry is played by famous magician Teller from the duo Penn and Teller. The knife trick that Amy's dad performs at the end is actually one of Teller's own.

For the first time since The Bon Voyage Reaction (2013), Raj needed alcohol to talk to a woman.

The selfie made by Sheldon appears at the end of the credits as Chuck Lorre's Vanity Card.

Title reference: Raj and Anu want to consummate their relationship, but it doesn't go exactly as planned.

S12E07 - The Grant Allocation Derivation (Notes and Trivia)

Penny says that Leonard thinks she has seen all Star Wars movies, even though she only saw "the one with the gold robot"; Bernadette then responds that it could be any of them. They are referring to the android C-3PO, who was indeed in all main Star Wars movies, but he didn't always have gold plating: in Star Wars: Episode I - The Phantom Menace (1999), he had no plating at all, and in Star Wars: Episode II - Attack of the Clones (2002), he had silver plating.

S12E06 - The Imitation Perturbation (Notes and Trivia)

Leonard mentions that the original Michael Myers mask used in John Carpenter's Halloween (1978) was a Captain Kirk mask turned inside-out. This isn't entirely correct. It wasn't turned inside-out, it was painted white, the hair was dyed brown, and the eyebrows were removed.

This final season Halloween episode is the fourth overall, after The Middle Earth Paradigm (2007), The Good Guy Fluctuation (2011), and The Holographic Excitation (2012).

When Howard (Simon Helberg) walks into the cafeteria dressed as Sheldon, the reactions from actors Johnny Galecki(Leonard) and Kunal Nayyar(Rajesh) were genuine. They had not seen Helberg in costume prior to this moment and their reactions made the final cut.

S12E05 - The Planetarium Collision (Notes and Trivia)

Final appearance of Bob Newhart as Arthur Jeffries/Professor Proton. In his previous episode The Proton Regeneration (2017), Newhart also appeared in Sheldon's dream on Dagobah, expressing his wish to meet in a deli while eating a pastrami sandwich. His wish has been granted here.

Title reference: Raj and Howard get into a conflict when Howard is asked to appear on Raj's planetarium show.

S12E04 - The Tam Turbulence (Notes and Trivia)

Amy and Sheldon's Relationship Agreement has apparently been upgraded into a Marriage Contract.

Entries on Sheldon's enemies list revealed in this episode: Tam for not moving with him to California; Jim Henson for creating Big Bird (Sheldon is mortally afraid of birds); the cafeteria lady for not revealing what's in the chili; and his brother George for peeing in his shampoo bottle.

Title reference: a visit from Sheldon's childhood friend Tam upsets things.

S12E03 - The Procreation Calculation (Notes and Trivia)

The Batmobile that Leonard gets to drive is a replica that was built for the TV movie Return to the Batcave: The Misadventures of Adam and Burt (2003).

Title reference: A compatibility questionnaire reveals that Penny and Leonard have different ideas about wanting kids or not.

S12E02 - The Wedding Gift Wormhole (Notes and Trivia)

Raj's father shows him a picture of his new girlfriend. The lady in the picture is Neha Kapur, the wife of Kunal Nayyar.

Sheldon and Amy return to the coffee shop where they first met in The Lunar Excitation (2010).

Title reference: a mysterious wedding gift from Penny and Leonard puts Amy and Sheldon on a strange journey.

S12E01 - The Conjugal Configuration (Notes and Trivia)

Title reference: Sheldon and Amy need to find a new way to deal with Sheldon's schedules in order to make their marriage work.

S11E24 - The Bow Tie Asymmetry (Notes and Trivia)

According to the producers, the role of Amy's father Larry was not written with the plan or idea of Teller playing the part. It was only upon the script's being finalized when the producers realized that Teller would be the perfect person for the part.

Courtney Henggeler (Missy Cooper) was actually pregnant in real life at the time of the taping of this episode.

Mark Hamill does have a dog in real life, but it is not the dog used. His actual dog, who's named Millie and not Bark, was not allowed to be used per union rules. Therefore he used an acting dog, and made up the idea of the fans naming his dog online as for why it's named "Bark Hamill".

Mark Hamill is besieged by questions about specifics of Star Wars about which he has no clue. This reflects his real life. In many interviews and encounters Hamill admitted that he hasn't an in-depth knowledge of the Star Wars universe, and how he often has no answers to the questions he gets from the fans. Hamill, jokingly, revealed how he even flunks tests about Star Wars given to him by his family, and that his sons and daughter know about Star Wars much more than him.

The new Avenger movie that Raj mentions is Avengers: Infinity War (2018), which was released on April 23, 2018, one day before this episode was taped, and 17 days before it was aired on May 10, 2018. This last date was also one week before the wedding between Prince Harry and Meghan Markle.

The running gag of people talking to Mr. Fowler, only for Mrs. Fowler to cut him off before he can speak, is an in-joke to Teller's magic/comedy act with Penn Jillette; Jillette is the more loquacious of the two, and Teller rarely, if ever, speaks. His silence stems from his youth when he performed at college frat parties; he found that by refraining from speaking, the audience was less likely to heckle him and more likely to pay attention to his act.

The tiara Amy wears is the same one Sheldon gave her in The Shiny Trinket Maneuver (2012).

This is the final appearance of Mary Cooper.

Title reference: Sheldon struggling with the asymmetry of his bow tie ribbon gives him the idea he needs for his big scientific breakthrough.

Wil Wheaton and Jerry O'Connell appeared together in the film Stand by Me (1986).

S11E23 - The Sibling Realignment (Notes and Trivia)

Chuck Lorre's Vanity Card #264 after the credits is a joke about about a guy who goes into a dentist's office, saying that he is a moth. The dentist tells him to see a psychiatrist, not a dentist; the guy says, "I saw a psychiatrist." The dentist then asks what he is doing here, but as the guy starts to respond, the card then reads that the punchline of the joke can be found on Vanity Card #265 at the end of that night's episode Summer Sausage, a Pocket Poncho, and Tony Danza (2018). That card simply read "Your light was on."

Jerry O'Connell who plays Georgie Cooper is supposed to be Sheldon's older brother by several years. In real life, O'Connell is actually about 1 year younger than Jim Parsons who plays Sheldon.

Raj mentions his brother Adoot, so between him and his sister Priya Koothrappali, two of Raj's five siblings have now been mentioned by name in the series. The names of his remaining two brothers and one sister are never revealed.

Title reference: Sheldon needs to straighten out his relationship with his brother George.

S11E22 - The Monetary Insufficiency (Notes and Trivia)

This episode marks the reappearance of President Seibert (Joshua Malina) after The Rothman Disintegration (2012), a span of 149 episodes.

Title reference: Sheldon is trying to raise money to conduct an experiment to prove his string theory research.

S11E21 - The Comet Polarization (Notes and Trivia)

Amy's actions to make the rooftop pigeon-free for Sheldon shows that he still hasn't gotten rid of his fear of birds, despite the progress he made in The Ornithophobia Diffusion (2011).

First appearance of Lauren Lapkus as Denise.

Ironically, Howard doesn't recognize Neil Gaiman, even though he is one of his favorite authors and one of the 'Neils' that he named his son after in The Neonatal Nomenclature (2018).

Raj's telescope is a popular model of Schmidt-Cassegrain design. The brand name, "CELESTRON," is partially concealed so that it appears to be "LESTRO."

This episode marks a significant change in fortune for Stuart. His store becomes more successful and he later starts dating, eventually moving in with, his newly hired assistant manager, Denise.

Title reference: Two opposite camps are created when Raj and Penny clash over the naming of a newly discovered comet.

S11E20 - The Reclusive Potential (Notes and Trivia)

Dr. Wolcott asks Sheldon is he is familiar with non-abelian group theory. In The Higgs Boson Observation (2012), Penny found a paper written by a five-year-old Sheldon dealing with abelian groups.

Title reference: Sheldon sees potential in becoming a reclusive scientist, thinking that the isolation and lack of distraction will help him make his big scientific breakthrough.

S11E19 - The Tenant Disassociation (Notes and Trivia)

Mrs. Petrescu (Michelle Arthur) was seen before during Sheldon and Amy's brunch in The Fetal Kick Catalyst (2016).

Sheldon's shirt in the episode contains robots from various TV shows and movies. They include: Daleks from Doctor Who, and R2-D2 from Star Wars.

This is the show's 250th episode.

Title reference: a play on the word 'tenant association', while also referring to the temporal disassociation (or separation) between Leonard and Sheldon as they battle each other for the presidency of said association.

S11E18 - The Gates Excitation (Notes and Trivia)

Although Penny hopes that doing a good job on giving Bill Gates a tour around her work may land her that PR job that she really wants, the PR job is never spoken of again.

Chuck Lorre's Vanity Card at the end of the credits commemorates the passing of frequent guest character Stephen Hawking, who had died two weeks before this episode was aired in the USA.

The blue shirt Sheldon wears in the "giant panties" scene displays a graphical representation of the Fibonacci Sequence, wherein each succeeding digit is the sum of the two preceding digits i.e. 0112358 etc.

S11E17 - The Athenaeum Allocation (Notes and Trivia)

Just like Mrs. Wolowitz and his big sister Halley, Neil Michael Wolowitz is mostly heard but only rarely seen on-screen in the remainder of the series.

Sheldon says that he and Leonard have a combined IQ of 360.

Title reference: Sheldon and Leonard's efforts in trying to get the Athenaeum Club booked for the Shamy wedding.

S11E16 - The Neonatal Nomenclature (Notes and Trivia)

Howard and Bernadette's newborn son's first name is Neil, after Neil Armstrong (an astronaut, like Howard), Neil Diamond (Howard's favorite singer) and Neil Gaiman (an author famous for the Sandman comics). Gaiman would have a cameo later in the season, in The Comet Polarization (2018).

Ozymandias, as suggested by Sheldon as a name for a baby, would hold a nice additional meaning. He was an Egyptian Pharaoh (also known as Ramesses II) who was the subject of Percy Bysshe Shelley's poem 'Ozymandias' (known for the famous phrase "Look on my works, ye Mighty, and despair!"), but it is also the name of an important character from the popular Watchmen comic, and its adaptation, Watchmen (2009).

The Campaign for North Africa, which Sheldon brings over to try to play with Bernadette, is a real-life game that was released in 1978; it is considered one of the most difficult and longest games ever to be played. It's also considered a collector's item and a cult favorite to hardcore gamers. It is famous for the "Pasta rule", which requires for the Italians to consume more water for boiling their pasta.

Title reference: the group is thinking of names for their future children after Howard and Bernadette cannot agree on one for their son.

S11E15 - The Novelization Correlation (Notes and Trivia)

Title reference: Leonard struggles to find out which woman in his life correlates with a certain character in his novel.

Wil Wheaton's address numbers shown on his house when Howard and Sheldon go to see him is 1701 which is the number of the Enterprise on Star Trek: The Next Generation (1987).

S11E14 - The Separation Triangulation (Notes and Trivia)

There actually are TWO Arby's in Okinawa, one in Kadena air base, one in Camp Foster (both for service members only).

S11E13 - The Solo Oscillation (Notes and Trivia)

The Far Side comic panel that Sheldon and Amy refer to is a real one that features a child pushing a door that has a large sign that says "Pull." There is a sign in front of the building that says "Midvale School for the Gifted."

Title reference: Sheldon vacillates (oscillates) between working solo and working with Penny.

When Howard and Raj are rehearsing their music in Howard's living room, on the bookcase behind them are the Howard and Bernadette dolls that Howard made in The Cooper/Kripke Inversion (2013).

S11E12 - The Matrimonial Metric (Notes and Trivia)

This episode was taped on December 5, 2017, one day after Melissa Rauch had given birth to her daughter Sadie, which explains why she has only one scene where she is in bed.

Title reference: Amy and Sheldon use scientific measurements to decide who should fulfill which roles at their wedding ceremony.

S11E11 - The Celebration Reverberation (Notes and Trivia)

First time we see Raj's apartment over Bert's garage, after he moved from his old one in the previous season.

Melissa Rauch gave birth to her daughter Sadie on December 4, 2017, two weeks after this episode was filmed while production was on hiatus. Her lack of screen time in this episode was to give her some final rest for her real-life delivery. She came back after the winter break.

Title reference: the consequences of the celebration of both Amy and Halley's birthdays.

S11E10 - The Confidence Erosion (Notes and Trivia)

Sheldon for the second time gets upset that butterflies might be released at a wedding and he calls them "airborne worms". Penny mentioned it when she and Leonard were planning their wedding in The Commitment Determination (2015).

Sheldon mentions the new Star Wars movie is coming out, referring to Star Wars: Episode VIII - The Last Jedi (2017).

Sheldon wants his wedding vows to be in Klingon. In The Countdown Reflection (2012), he tried to do Howard and Bernadette's wedding speech in Klingon, and when told to do it in English, he mentioned that Klingon loses something in translation.

Title reference: Raj believes that Howard is eroding his confidence with his incessant pranking.

S11E09 - The Bitcoin Entanglement (Notes and Trivia)

Although it only appears in flashbacks, this is the final appearance of the original layout of Stuart's comic book store in the series. Also returning are Howard's old bedroom, Raj' inability to talk to women, and Penny's old apartment 4B before it was taken over by Sheldon and Amy.

Bernadette only appears onscreen during the flashback scenes. Only her voice is heard (over the baby monitor) in the real time scenes. In the flashback scenes, she is standing behind a counter, undoubtedly to hide Melissa Rauch's real-life pregnancy.

Carol Ann Susi, who voiced Howard's mother, died November 11, 2014, more than three years before this episode was aired, with her last appearance in The Prom Equivalency (2014). Howard's mother's voice in the flashback is hers though, consisting of audio re-used from previous episodes.

Sheldon telling Amy to get a dish so he can serve her some cold revenge is a reference to the Klingon proverb "Revenge is a dish best served cold" from Star Trek II: The Wrath of Khan (1982). The same proverb was also referred to by Sheldon in The Creepy Candy Coating Corollary (2009), when plotting his revenge against Wil Wheaton. In both cases, his set-up backfires significantly.

The Bitcoin Entanglement (2017) was advertised to include a major revelation about Leonard and Penny's relationship through the seven year old video left by a drunk Penny. She apologized to Leonard for breaking up with him in The Wheaton Recurrence (2010) because she loved him and was freaked out that someday they might get married and that it would be forever.

Title reference: a chaotic chain of events and memories is revealed when the boys are searching for their old Bitcoins.

S11E08 - The Tesla Recoil (Notes and Trivia)

Raj claims that Thomas Edison electrocuted the elephant Topsy. Topsy was killed in 1903 and her electrocution was filmed by the Edison film company. Thomas Edison does not seem to have even been present on Coney Island, where the electrocution took place, that day.

Title reference: Sheldon thinks of himself as a modern Tesla, and is shocked when his friends call him an Edison.

S11E07 - The Geology Methodology (Notes and Trivia)

Bernadette mentions that she still doesn't like Howard's juggling act. This alludes to The Closet Reconfiguration (2013), where Bernadette admitted that she had hidden Howard's juggling pins inside his overstocked closet.

Sheldon's way of knocking on doors has changed yet again: instead of calling the other person's name once each time he knocks on their door, here he calls Bert's name once on the first knock, twice on the second and three times on the third knock.

The cricketers Raj mentions at the bar, Ravichandran Ashwin, Hardik Pandya and Virat Kohli, are all real professional Indian cricket players.

Title reference: Sheldon starts working in the field of geology.

S11E06 - The Proton Regeneration (Notes and Trivia)

Behind Wil Wheaton, a model of a Star Wars speeder bike with scout trooper figure is visible. This reflects Wheaton's enthusiasm for the Star Wars franchise, which predates his role on Star Trek, and counters his taunt of the Star Wars moviegoers in The Opening Night Excitation (2015).

Bernadette is put on bed rest due to her pregnancy. This was probably done to give Melissa Rauch some rest as well, as she was almost seven months pregnant in real life.

Both Bob Newhart and Wil Wheaton make appearances, after being absent for the entire 10th season.

Halley makes her first 'appearance' of the season saying her first words. In keeping with Mrs. Wolowitz, Halley is mostly heard and kept off-screen.

Title reference: the revival of the Professor Proton show.

When Amy suggests that the next Professor Proton could be a woman, Sheldon responds that "you've already got "Doctor Who" and the Ghostbusters. Leave us something." Jodie Whittaker was announced as the first actress playing The Doctor almost three months before The Proton Regeneration was taped, and she made her first appearance in Twice Upon a Time (2017), almost two months after this episode was aired.

When Sheldon visits Wil Wheaton at home, Wil is wearing a tee shirt with a design on it similar to the opening theme song graphics.

S11E05 - The Collaboration Contamination (Notes and Trivia)

Amy and Howard seem to have a preference for singers called "Neil". In The Scavenger Vortex (2013), they discovered their shared love for Neil Diamond, and here, they enjoy listening to Neil Sedaka.

This is the first time Howard and Amy work together in the lab.

S11E04 - The Explosion Implosion (Notes and Trivia)

Howard and Bernadette's second child is revealed to be a boy.

On Howard's shelf, alongside the model rockets, are several model aircraft. They include, from left to right, NASA's SOFIA (Stratospheric Observatory for Infrared Astronomy) Boeing 747, a World War II US Army Air Forces C-47 with D-Day operational markings, a USAF T-38 trainer (a type of aircraft also used by NASA as a chase plane), and an AH-64 Apache attack helicopter.

This is the first time Sheldon is seen driving with an actual driver's license. He obtained a learner's permit in The Euclid Alternative (2008) and drove Penny to the hospital for an emergency in The Adhesive Duck Deficiency (2009), but always claimed that he never got a real driver's license. That is, until The Space Probe Disintegration (2015) where he admitted to Leonard that he had obtained a permit after Amy gave him lessons, but kept this quiet (even from Amy) since he prefers to be driven around.

S11E03 - The Relaxation Integration (Notes and Trivia)

Sheldon sits on the side of couch but not on his usual spot, even though it is vacant, showing how his laid-back persona is unconsciously forcing itself out.

The tune Sheldon plays on a flugelhorn in his dream is "Feels So Good" by Chuck Mangione.

S11E02 - The Retraction Reaction (Notes and Trivia)

Richard Feynman is really interred in Altadena, CA. He is buried at Mountain View Cemetery and Mausoleum, Founders Lawn, Lot 4390, Grave 11, Curb No. 1617.

Romulan Ale is a popular drink in the Star Trek universe. In the shows, there is an uneasy truce between planet Romulus and the Federation of Planets (of which Earth is a member), and like Cuban cigars, the drink is considered illegal in the Federation due to a trade embargo imposed on the Romulans (which, as Leonard mentions, was temporarily lifted during a brief alliance period). Romulan Ale is also somewhat akin to marijuana, as it is known for its rather extremely intoxicating properties, considered illegal except for "medicinal purposes", and despite all the prohibition, its acquisition, consumption and acceptance is relatively widespread among Federation members.

This is the third and final time that an interview with Ira Flatow causes a fuss, after Kripke used the opportunity to prank Sheldon in The Vengeance Formulation (2009), and after Sheldon believed that Flatow was mocking him in The Discovery Dissipation (2013).

S11E01 - The Proposal Proposal (Notes and Trivia)

After going shopping with Amy, Sheldon is seen in a Superman-themed button-down shirt worn over a long-sleeved t-shirt for the first time, instead of his signature style of a short-sleeved t-shirt worn over a long-sleeved t-shirt.

Bernadette is pregnant again because Melissa Rauch had become pregnant in real life. Her daughter Sadie was born December 4, 2017, meaning Rauch was about five months pregnant when the episode was filmed, and they had to hide her baby bump with clothing and objects.

Mary Cooper and Ramona Nowitzki return in this episode. For Riki Lindhome, who plays Ramona, it is her final appearance on the show.

This was Stephen Hawking's last guest role, almost half a year before his death on March 14, 2018.

S10E24 - The Long Distance Dissonance (Notes and Trivia)

According to Mayim Bialik, tears are spilled in the rehearsal of the last scene.

Amy's room at Princeton seems to be the same as her former apartment.

On the plane to Princeton, Sheldon watches SpongeBob SquarePants episode "Jellyfishing/Plankton!" (1999).

Ramona Nowitzki (Riki Lindhome) makes a return after her previous appearance in The Cooper-Nowitzki Theorem (2008), 208 episodes ago.

When Penny and Bernadette are talking about Dr. Nowitzki, Penny acts as if she's never met her. But in The Cooper-Nowitzki Theorem (2008), Penny had a few encounters with Dr. Nowitzki (when she was giving Sheldon a pedicure, when she admonished Penny for distracting Sheldon, and when she storms out when Sheldon won't add her name to his theorem).

S10E23 - The Gyroscopic Collapse (Notes and Trivia)

Apartment 3A (the apartment below Leonard's) is shown to be empty. This implies that Mrs. Gunderson, who appeared in The Lunar Excitation (2010), no longer lives there.

It turns out that Zack (Brian Thomas Smith), Penny's dimwitted ex-boyfriend, was right for a change, when he told the boys in The Fermentation Bifurcation (2016) that the military might try to take control of the their guidance system, and expressed disbelief that the boys hadn't considered this scenario.

The story in this episode has similarities to the story of the film Real Genius (1985). In both stories a group of young scientists invents a small device which they hope will be used for good but which is scooped up by the military for use as a weapon. In both stories it is an outsider of each group that suspects the government's intentions. The conclusions of the two stories are very different.

Title reference: Leonard, Sheldon and Howard's gyroscope project ends when the government takes it out of their hands.

S10E22 - The Cognition Regeneration (Notes and Trivia)

Another one of her many talents, actress Melissa Rauch actually did her own ventriloquism in the scene where she has Tammy Jo St. Cloud talk to her husband, Howard.

Despite scenes set at the Comic Book Store and the Wolowitz's residence, Stuart (Kevin Sussman) is absent from this episode. However, Brian Thomas Smith, a previous regular guest star, makes another appearance as Zack, his first since The Fermentation Bifurcation (2016) a year before.

Oddly, and for the first time in the whole series, a previously used Vanity Card is displayed (#552 from The Allowance Evaporation (2017)).

Sheldon and Amy discuss the likelihood of him winning a Nobel Prize before he turns 40. This is, in fact, how the series ends, with them sharing the accolade for their joint research.

S10E21 - The Separation Agitation (Notes and Trivia)

Sheldon's physicist joke about Feynman, Einstein and Schr?dinger in a bar refers to their specific theories about reality. Feynman was known for his simple visual representations of complex mathematical expressions ("It appears we're inside a joke"); Einstein's theory of Special Relativity states that synchronous movement of objects depends on who is observing these movements ("But only to an observer who saw us walk in simultaneously"). The thought experiment of 'Schr?dinger's cat' (mentioned on the show several times since The Tangerine Factor (2008)) describes a cat in a closed box with a vial of poison set to break at an unknown time; the only way to know for certain if the cat has died is by looking inside the box ("If someone is looking in the window, I'm leaving"). Sheldon's joke about Heisenberg being told he was going 85 miles per hour refers to the 'Heisenberg Uncertainty Principle', or the inability to measure both an object's location and speed in one observation ("Darn it, now I don't know where I am").

Title reference: the difficulty that Howard, Bernadette and Stuart experience when being separated from Halley while she is at daycare.

S10E20 - The Recollection Dissipation (Notes and Trivia)

In addition to English, Amy and Sheldon apparently have at least rudimentary skills in German, Mandarin, and Navajo. Sheldon and Amy could previously be seen making attempts at speaking German during their first "Fun With Flags" webisode in The Beta Test Initiation (2012). Sheldon was learning to speak Mandarin (poorly) during The Tangerine Factor (2008), and later recognized the tattoo on Penny's buttocks as the Chinese symbol for "soup" in The Adhesive Duck Deficiency (2009), so he may have used his knowledge to translate "Soft Kitty" into the language.

In addition to playing a floor harp, Amy apparently also has at least a rudimentary mastery of the zither, or auto-harp.

Penny used to stop for a bear claw during her morning run The Cruciferous Vegetable Amplification (2010) but now she stops for a doughnut.

Title reference: Sheldon losing his memory.

S10E19 - The Collaboration Fluctuation (Notes and Trivia)

Sheldon is very happy with Amy's list of fair topics for insult, which include educational pedigree, scientific field and intellectual prowess. Not surprisingly, these happen to be the areas where Sheldon excels at: he often belittles Howard's engineering education, has nothing but contempt for geologists, and constantly questions Leonard's intelligence.

Title reference: the cooperation between Sheldon and Amy, which fluctuates between working together and insulting each other.

S10E18 - The Escape Hatch Identification (Notes and Trivia)

Stuart has a baseball bat with barbed wire wrapped around it, a nod to The Walking Dead (2010), where Negan wields a baseball bat, named Lucille, in a very aggressive fashion.

The model aircraft in Howard and Bernadette's living room, in front of the window, is a Bombardier Challenger CL-600 series business jet.

S10E17 - The Comic-Con Conundrum (Notes and Trivia)

In the scenes at Bernadette and Howard's house Stuart is seen wearing a gray t-shirt with the Ubuntu Linux distribution logo on it. Appropriately this logo is called "Circle of Friends".

Raj is wearing his Aquaman costume from The Justice League Recombination (2010).

S10E16 - The Allowance Evaporation (Notes and Trivia)

A very rare (if not unique) view of the fourth wall of the stairs, exactly the third floor hall, is shown at 9:10.

Howard mentions he brought imported beer. The beer he and Leonard are drinking is Hoegaarden which is made in Belgium

It is established that Raj's favorite movie is The Princess Bride (1987). Raj has previously shown his infatuation with this movie: in The Workplace Proximity (2013), he and Howard spent the night "giggling, eating cookie dough, and watching The Princess Bride"; when Howard told Raj to stop talking, Raj replied with "As you wish", which, in that movie, was a veiled way of saying "I love you". In The Workplace Proximity (2013), Raj imagined fencing to be like Game of Thrones (2011), but when Howard suggested Princess Bride, Raj immediately changed his answer to that. Later, Raj emulated the famous line from the movie, "My name is Inigo Montoya. You killed my father. Prepare to die."

It is revealed here that Sheldon has had his driver's license for two years now, but lets himself be driven around because it makes him feel important.

Raj holds his breath for 1 min. 28 sec.

This is the shortest episode in the series.

Title reference: Raj finally stops the allowance he is getting from his father.

When Amy tells Sheldon that it is customary to greet a familiar person in a restaurant, Sheldon responds that he has several restraining orders that say otherwise. At this point in the series, Sheldon has restraining orders from Carl Sagan, Leonard Nimoy, Stan Lee, Bill Nye and, as revealed in this episode, Zachary Quinto. It was stated in The Love Spell Potential (2013) that Sheldon was initially worried about Quinto being "the new Spock", but he apparently ended up liking him so much that he once followed him into a bathroom.

S10E15 - The Locomotion Reverberation (Notes and Trivia)

The diesel engine Sheldon works on is a Detroit Diesel 6V71. While not used in trains as he suggests, the 71 series is one of the most prolific marine diesels in existence.

The Nevada Northern Railway is an actual, operating railroad museum in Ely, Nevada (which really is 4 hours from any major airport!), and does offer rides, including allowing you to play engineer and operate the throttle on the moving train.

The shower curtain with the periodic table on it that was always hanging in the bathroom of apartment 4A (Sheldon and Leonard's former apartment) is now seen hanging in apartment 4B (Penny's old room) for the first time. Sheldon probably didn't bring it along when he moved his possessions in The Property Division Collision (2016), because Penny's old curtain could still be briefly seen while Amy was trying to seduce him in her wizard robes in The Birthday Synchronicity (2016). He must have retrieved it somewhere between episode 11 and 15.

The song playing during Amy's fantasy is "Rock You Like A Hurricane" by Scorpions.

S10E14 - The Emotion Detection Automation (Notes and Trivia)

This episode features appearances of several (regular) guest actors who all played Raj' girlfriends: Kate Micucci as Lucy (last seen 78 episodes ago in The Itchy Brain Simulation (2013)); Laura Spencer as Emily Sweeney (last seen 20 episodes ago in The Application Deterioration (2016)); Alessandra Torresani as Claire (last seen 16 episodes ago in The Fermentation Bifurcation (2016)); and Katie Leclerc, who made one previous appearance as Deaf Emily in The Wiggly Finger Catalyst (2011). This is also the last appearance of all four characters in the series.

Title Reference: Sheldon uses a machine to detect people's emotional levels.

S10E13 - The Romance Recalibration (Notes and Trivia)

Leonard quotes some lyrics from "(God Must Have Spent) A Little More Time On You" by *NSYNC, which was identified as Penny's favorite boyband in The Platonic Permutation (2015).

Title Reference: Leonard and Penny reconsider their married romantic relationship.

S10E12 - The Holiday Summation (Notes and Trivia)

The episode won an Emmy Award for Outstanding Multi-Camera Picture Editing for a Comedy Series.

The name of the man working at Sparkletts wearing an eye patch (the one that Sheldon asked if he could look behind it) mentioned in The Separation Oscillation (2015), is revealed to be Omar.

The T-shirt Sheldon is wearing with a waveform on it is actually from an poorly maintained vinyl recording. You can see at least five scratch high points on it. There would be no scratches if the sound file came from a CD.

This is the sixth Christmas episode in the series; the others are The Bath Item Gift Hypothesis (2008), The Maternal Congruence (2009), The Santa Simulation (2012), The Cooper Extraction (2013), and The Clean Room Infiltration (2014),

We learn from Stuart that he has a brother and sister, and that he still has a grandmother, even though he said in The Friendship Contraction (2012) that his grandparents were dead.

S10E11 - The Birthday Synchronicity (Notes and Trivia)

Baby Halley's cries are voiced by Pamela Adlon, who was a friend of Carol Ann Susi who voiced Howard's mother, Mrs. Wolowitz, until she passed away in 2014. Adlon was briefly considered to take over the role of Mrs. Wolowitz before it was decided to have the character pass away in the show as well, although Adlon did later voice Mrs. Wolowitz in A Swedish Science Thing and the Equation for Toast (2019).

Howard and Bernadette name their daughter Halley, after Halley's comet. Appropriately, her father Howard is an astronaut, and her godfather Raj is an astrophysicist.

In keeping with the tradition of never showing the late Mrs. Wolowitz in full on screen, Howard and Bernadette's baby Halley is only heard but never seen in the show either, until the final episode.

Title Reference: the birthdays of Amy and Halley (Howard and Bernadette's newborn) falling on the same day, December 17.

S10E10 - The Property Division Collision (Notes and Trivia)

Amy's portrait of her and Penny was first seen in The Rothman Disintegration (2012).

Bernadette heads to the hospital to have her baby.

The salt & pepper shakers in Howard and Bernadette's house are the same as the ones found in Leonard and Sheldon's apartment.

Title Reference: The title refers to Leonard and Sheldon's dispute over dividing their property.

S10E09 - The Geology Elevation (Notes and Trivia)

Bert's full name is Bertram Kibbler.

Professor Stephen Hawking mentions he has been on "Star Trek" and "The Simpsons". He indeed appeared as a hologram of himself in "Descent (1993)" and voiced himself in four episodes of "The Simpsons (1989)". He also appeared in "Futurama (1999)", which was made by the creators of "The Simpsons".

Sheldon seems to have an obsession with the MacArthur Genius Grant, since one of his Roommate Agreement clauses even states that if either he or Leonard wins it, he has to mention the other in his acceptance speech (The Large Hadron Collision (2010)). The fact that Sheldon is jealous of a geologist for winning the grant is poetic justice for his well-established disdain for that field of science. And when Sheldon compliments Leonard for never getting jealous, he forgets that Leonard was insanely jealous of David Underhill in The Bath Item Gift Hypothesis (2008), ironically because Underhill had won the MacArthur Grant as well.

The episode title refers to Bert's geology research getting more attention than Sheldon's work.

The remark about Penny's short hair in season 8 is probably a jab at the fact that most of Kaley Cuoco's fans didn't like her new hair style, which returned to its normal length in season 9.

This show is taped in the Warner Brothers Studios sound stage 25. Sheldon and Bert visit the set of "The Ellen DeGeneres Show (2003)", taped in stages 1-3.

S10E08 - The Brain Bowl Incubation (Notes and Trivia)

Chuck Lorre's Vanity Cards simply stating "Uh-oh" was in reference to Donald Trump winning the 2016 Presidential Elections three days before the episode was broadcast.

Raj mentions his sister being a lawyer, a reference to Priya, who was last seen in The Good Guy Fluctuation (2011) and last mentioned in The Recombination Hypothesis (2012).

Title Reference: Sheldon and Amy mix their DNA and incubate some brain cells.

S10E07 - The Veracity Elasticity (Notes and Trivia)

Sheldon asks Amy to sing 2001: A Space Odyssey (1968). The proper name is 'Also sprach Zarathustra', also known as Opus 30 by Richard Strauss.

This episode was the last one broadcast prior to the 2016 Presidential Elections between Hillary Clinton and Donald Trump, which were won by the latter. All of Chuck Lorre's Vanity Cards starting with this episode and ending with The Romance Recalibration (2017) comment on the election and the result.

Title Reference: Amy stretching the truth about her old apartment being repaired.

Ubbi Dubbi, spoken by Penny and Amy in this episode, was popularized by the 1970's children's show Zoom (1972). In this secret language, the letters "ub" are added in front of each vowel sound in every syllable of an existing word, e.g. "hello" becomes "huballubo". It may also have been the inspiration for Amy's invented language 'Op' from The Skank Reflex Analysis (2011), where the letters "op" are added to each consonant in a word (so "hallo" would become "hop-a-lop-lop-o").

When Penny tells Leonard she can make do with just the candle she holds up her left hand. Her ring & pinky fingernails are polished a darker color while the rest appear to have a sheer clear coat of polish.

S10E06 - The Fetal Kick Catalyst (Notes and Trivia)

At the Van Nuys Comic-con, the table to Penny and Leonard's left is that of David Gerrold. He is a Hugo and Nebula award-winning American science fiction screenwriter and novelist. He wrote the Star Trek (1966) story The Trouble with Tribbles (1967) as well as dozens of novels, short stories, and TV scripts. He seems to be selling Tribbles at his table.

Leonard says that he once paid $20 for Theo Sassler's autograph, even though he didn't know who he was (he just liked the name). For the record, there is no celebrity named Theo Sassler in real life, it was just an invented name for the script.

Penny's name on the 'Serial Ape-ist' posters at the movie convention is cleverly hidden so not to reveal her surname.

The convention table to Penny's right features Alex Ross' art work on the back wall, so it may have been in the works to have him do a cameo, or it may have simply been a means to feature a notable name and justify the "ComicCon" part of the name.

The credits on the posters for Serial Ape-ist and Serial Ape-sit 2 list the director's credits to Nikki Lorre, who is the daughter of Big Bang Theory creator Chuck Lorre. This implies that the male British director of the sequel who fired both Penny and Wil Wheaton in The Gorilla Dissolution (2014) was eventually fired himself, or quit the movie.

When discussing their party, Sheldon says "I hope it's not a West Coast party, 'cause according to the man on the radio, a West Coast party don't stop." He is referencing lyrics to the song "1, 2, 3, 4 (Sumpin' New)" by Coolio.

S10E05 - The Hot Tub Contamination (Notes and Trivia)

An explanation is finally given for Sheldon's signature knock; he has had it since age 13 when he caught his father in bed with another woman, and it is to give people behind the door time to get their pants on.

S10E04 - The Cohabitation Experimentation (Notes and Trivia)

Sheldon saying to Amy, "You truly are a Goofus to my Gallant," is a reference to Highlights Magazine, a monthly magazine for children. The Goofus and Gallant comics were intended to teach good manners and social behavior. Gallant is polite, considerate, and generous. Goofus is selfish, rude, inconsiderate, and bossy.

S10E03 - The Dependence Transcendence (Notes and Trivia)

For the first time in the series, Sheldon admits he can't solve a math problem.

The Flash says that he stays in business because he bought stock in Marvel. This plays fun at the fact that The Flash is from Marvel's biggest competitor, DC Comics, whose cinematic adaptations did significantly less box office than Marvel's at the time.

S10E02 - The Military Miniaturization (Notes and Trivia)

Leonard mentioned that the retina scanner worked without him having to take his glasses off. Ironically, his glass have no lenses.

Sheldon mentions the rediscovery of the Oobius depressus wasp after 101 years. The wasp was collected in traps set in the Midwest between August and October of 2015. The discovery was verified by the UC Riverside Entomology Research Museum in June 2016.

S10E01 - The Conjugal Conjecture (Notes and Trivia)

This is one of, if not the only, episode with the most guest stars. Penny had 3 family members (Katey Sagal, Keith Carradine, Jack McBrayer); Leonard has 2 (Judd Hirsch and Christine Baranski); and Sheldon's mother played by Laurie Metcalf. Dean Norris also begins a multiepisode run as Colonel Richard Williams.

This is the second consecutive season that begins with Leonard and Penny getting married.

This will be the second series in which Katey Sagal will play Kaley Cuoco's mother. The first one was 8 Simple Rules (2002).

S09E24 - The Convergence Convergence (Notes and Trivia)

Johnny Galecki had met Judd Hirsch at the James Burrows tribute show long before this episode, and had personally asked him to play Leonard's father. Galecki really wanted Hirsch since he had already patterned Leonard after Hirsch' character Alex Reiger from Taxi (1978), who was also one of the more normal people in a group of crazies.

Judd Hirsch, who plays the father of physicist, Leonard Hofstadter, has a degree in physics. He earned it from the City College of New York, circa 1956.

The cop that pulls Howard over is played by the same actor, Marcus Folmar, who played the mall security guard in The Hesitation Ramification (2014). Raj & Stuart were at the mall to practice talking to girls but the guard was the only stranger Raj spoke to. He asked if the guy liked being a mall security guard.

The pink photo frame with the picture of Penny's old car that she gave to Leonard in The Expedition Approximation (2014) can be seen in Leonard's bedroom.

Title Reference: The episode features two coming-togethers ('convergence'): the group gathers together with Leonard and Sheldon's parents, and Leonard's father and Sheldon's mother have their own special get-together.

S09E23 - The Line Substitution Solution (Notes and Trivia)

The "new Avengers movie" that the guys are waiting in line for is Captain America: Civil War (2016). Technically it isn't an Avengers movie, although it was nicknamed "Avengers: Part 2.5" by the fans since all regular Avengers characters were in it, except for Thor and the Hulk. The Q&A session with Joss Whedon is a bit strange since Whedon had no affiliation with this movie (although he did direct the previous Avenger movie, Avengers: Age of Ultron (2015), that Sheldon has some questions about). ETA: Q and A sessions typically take place several months or a year after a movie has been released, therefore the gang is waiting to discuss Avengers: Age of Ultron, which released a year earlier.

This is the first time that Beverly appears on the show without sharing a scene with Leonard, the first time that she appears in Penny's apartment, and the first time she has a conversation with Amy and Bernadette.

S09E22 - The Fermentation Bifurcation (Notes and Trivia)

Amy says that she and Howard last spent time together three years ago. This is a reference to the seventh season episode The Scavenger Vortex (2013) that was aired 2.5 years before: it refers to when the two were paired together for the scavenger hunt created by Raj, or the Neil Diamond concert the two said they should go to.

Penny's ex-boyfriend Zach (Brian Thomas Smith) makes his first appearance since season 7's The Cooper Extraction (2013).

S09E21 - The Viewing Party Combustion (Notes and Trivia)

Sheldon is frustrated with writer George R.R. Martin because Martin couldn't keep up his writing with the pace of Game of Thrones (2011), so Sheldon is no longer able to spoil the show for Leonard with his knowledge from the books. At the time of the episode, the TV series had indeed caught up with 'A Dance with Dragons', which was then the most recently released book in Martin's 'A Song of Ice and Fire' book series. Sheldon actually voices the frustration of many fans of the books who had already been waiting five years for the release of the next book, 'The Winds of Winter', as Martin kept missing his deadlines. By the time that The Big Bang Theory (2007) and Game of Thrones (2011) ended (both in 2019), the book was still not released.

The Game of Thrones (2011) episode the group is getting ready to watch is The Red Woman (2016). Stuart has dressed himself up as the character Jon Snow (Kit Harington) from that series.

Title Reference: Refers to the party organized by the group to watch Game of Thrones (2011) and how it results in heated arguments.

S09E20 - The Big Bear Precipitation (Notes and Trivia)

At the cabin, as always, Sheldon is sitting in his traditional spot: on the right seat of a couch that sits in the middle of the room.

The cabin used that Penny, Leonard, Sheldon and Amy go to for the weekend is filmed on the same set used in an episode of 2 Broke Girls (2011) when they unknowingly join a cult.

The cabin was also used as the Forrester Big Bear cabin in The Bold and the Beautiful (1987).

The episode title "The Big Bear Precipitation" refers directly to the location of the cabin, Big Bear, and the fact that it rains (precipitation meaning falling water particles). However, the title also refers to the large teddy bear that Raj impulsively buys for the Wolowitz family (precipitation meaning rashness). Precipitation can also mean "the fallout" or results of something, in this case, the revelation of Leonard's bank account and Penny's dislike of her work. Discovery of the bank account is the fallout of playing the game.

S09E19 - The Solder Excursion Diversion (Notes and Trivia)

In Sheldon's storage unit you can see a box of the "Happy Guy" computer that Penny suggested Sheldon buy for Leonard in The Peanut Reaction (2008).

Title Reference: The title is a reference to Howard and Leonard being diverted by the free upcoming movie screening during their 'excursion' to the hardware store to pick up the solder.

S09E18 - The Application Deterioration (Notes and Trivia)

It is revealed that Howard is a federal NASA employee on loan to Cal Tech.

It's revealed that Sheldon does his contracts using his own proprietary font "Shelvetica".

Sheldon's T-shirt is a reference to the origin of DC Comics' "The Flash", who gained super-speed when he was doused in a mixture of electrified chemicals after lightning struck his laboratory.

Title reference: the patent application for their invention causes a temporal deterioration in the relationship between Howard, Leonard and Sheldon.

S09E17 - The Celebration Experimentation (Notes and Trivia)

Leslie Winkle returns and makes a special guest appearance. She was never mentioned between her previous appearance, season 3's The Lunar Excitation (2010), and this episode.

Sheldon says that for music, he would like Tibetan throat singing. Sheldon himself showed his talent for Tuvan throat singing in The Large Hadron Collision (2010).

Since this is the 200th episode in the series, rumors circulated for weeks as to which celebrities would appear as guest stars on the episode.

With Leonard, Penny and Leslie Winkle present in one room, it reunites Leonard with two of his love interests on the show (one current, one former), as well as Johnny Galecki with two of his real-life ex-girlfriends (Kaley Cuoco and Sara Gilbert).

S09E16 - The Positive Negative Reaction (Notes and Trivia)

Bernadette says she and Howard conceived Halley when they had sex in Sheldon's bed. Karma comes back around in The Celebration Reverberation (2017) when Amy and Sheldon plan to have coitus in one of the empty beds at Howard and Bernadette's home after they jump in the bouncy house at the end of the episode.

Sheldon reveals that he shaves once every eleven days.

This is the first episode this season where the whole gang are in the same scene together.

S09E15 - The Valentino Submergence (Notes and Trivia)

Bernadette reveals that she is pregnant.

Sheldon mentions during fun with flags that New Zealand is proposing a new flag. This is in reference to the John Key-led flag referendum (2015-16), which failed to replace the existing flag.

S09E14 - The Meemaw Materialization (Notes and Trivia)

Meemaw wonders why Penny and Leonard know about Sheldon's nickname "Moonpie" (because he's nummy-nummy and she could just eat him up), while Amy doesn't. The reason is that Penny had to search for Sheldon's flash drive in The Terminator Decoupling (2009), and found a letter from Meemaw where she called him Moonpie. She then made him explain the meaning of the term in exchange for her help.

This is the first (and only) on screen appearance of June Squibb as Sheldon's grandmother, otherwise known as Meemaw.

S09E13 - The Empathy Optimization (Notes and Trivia)

Amy is still away at a convention and only shows up in a few brief scenes on a monitor in this episode and the previous one, so that Mayim Bialik could take some time off from the show.

Title Reference: Sheldon learning about the best way to be empathetic.

S09E12 - The Sales Call Sublimation (Notes and Trivia)

Sheldon and Raj name the asteroid they discover after Amy. In real life there's an asteroid named for Sheldon: 246247 Sheldoncooper, discovered on September 20, 2007.

S09E11 - The Opening Night Excitation (Notes and Trivia)

In a geeky reference to Star Wars there is a scene between Sheldon's bedroom and Amy's bedroom where the scene change swipes left to right which was a technique used in the original trilogy.

Star Wars' theme plays and displayed on the screen in Star Wars' opening crawl fashion: "Episode 194, The Opening Night Excitation, It is a period of great tension. Our heroes, Leonard, Sheldon, Wolowitz and Koothrappali know that tickets to the new Star Wars movie are about to be available for pre-sale. If they fail in their mission and can't see it on opening night, Sheldon has sworn they will never hear the end of it for the rest of their lives... They believe him."

The episode won an Emmy Award for Outstanding Multi-Camera Picture Editing for a Comedy Series.

The only episode where the episode title is shown on-screen.

When this episode was taped, Star Wars: Episode VII - The Force Awakens (2015) still hadn't been released, so the writers were taking a chance by having the characters declare that it was a great movie (especially considering the negative reactions to the previous Star Wars prequel films). Fortunately, the movie got very good reviews after its release.

S09E10 - The Earworm Reverberation (Notes and Trivia)

Avogadro's constant, displayed on Dave's tie clip, is a number: 602,214,076,000,000,000,000,000 to be exact. Dave states that it helps calculate the number of atoms in a substance, but this isn't entirely correct: it calculates the number of particles in a given substance, which, depending on the substance, can be atoms but also entire molecules.

There is a real United Nations Office for Outer Space Affairs (UNOOSA), but it is the United Nations office responsible for promoting international cooperation in the peaceful uses of outer space, not one dedicated to contact with extraterrestrial life.

S09E09 - The Platonic Permutation (Notes and Trivia)

This is the third episode in the entire series that does not end with a punch line or any audience laughter; the other two being The Comic Book Store Regeneration (2015) and The Commitment Determination (2015). This episode does end with a punchline and laughter .

Title Reference: The title refers to Sheldon and Amy reestablishing their platonic relationship.

S09E08 - The Mystery Date Observation (Notes and Trivia)

Part of this was shot on the Warner Bros lot, the lot is known for being used as the exterior scenes of Stars Hollow on Gilmore Girls (2000). The restaurant where Amy and her date are eating was originally used as Doose's Market in the show.

The turquoise t-shirt Sheldon is wearing when he meets the contest winner appears to display the Green Lantern oath, written in Interlac, the language used by the Legion of Super-Heroes.

The whiteboard next to Sheldon's door shows two implicit functions (y^2=x^3-x and y^2=x^3-x+1) and what appears to be sketches of their graphs. Both are correct.

This is Lio Tipton's second appearance on the show, having first appeared as herself in The Panty Pi?ata Polarization (2008) as one of the models from America's Next Top Model (2003) tracked down by Howard and Raj.

Title Reference: The title refers to Penny, Bernadette and Leonard spying on Amy's date.

When Raj realizes their online challenge has succeeded, he yells out, "We are the dreamers of dreams." The original source of this may be the first stanza of a poem called "Ode" by Arthur O'Shaughnessy. The first two lines are also quoted by the candy maker in Willy Wonka & the Chocolate Factory (1971).

S09E07 - The Spock Resonance (Notes and Trivia)

Only acting credit for Adam Nimoy, son of the late Leonard Nimoy (who had featured in the show in The Transporter Malfunction (2012)). Adam has mostly worked as a copyright lawyer and a TV director, and has appeared as himself in a number of documentaries.

The clip is from Star Trek (1966) is from Where No Man Has Gone Before (1966).

The documentary about Spock that is being filmed in this episode is a genuine title called For the Love of Spock (2016). In addition to clips from this episode being shown in the documentary, Jim Parsons, Bill Prady and Mayim Bialik were all interviewed for it.

The Vulcan phrase used by Sheldon ("Kup-fun-tor ha'kiv na'ish du stau?") to say that there is no use to dwell on things that have passed literally means "Can you return life to what you kill?" When Penny asks Leonard if he knows what it means, he replies with "No". When she asks him if he's telling the truth, he responds with "Nirsh" ("No"). At the end, when Sheldon says that if Amy rejects his marriage proposal, she can just "ponfo mirann", it means "go to hell". It is interesting to note that the Vulcan language from Star Trek lore isn't as well developed as the Klingon language, for which an entire grammar and vocabulary was conceived.

Title Reference: The title refers to the continuing importance that the character Spock has on Sheldon, who is torn between his image as an emotionless person and his feelings for Amy. Also, the (real) documentary being filmed in the show, For the Love of Spock (2016), frequently mentions how much Spock resonates with people who feel like outsiders.

S09E06 - The Helium Insufficiency (Notes and Trivia)

Regarding liquid helium, reference is made to party supply stores and to the national reserve. Both of those sources have helium as a gas. The really hard part of making liquid helium is not obtaining the gas but getting it cold enough to liquefy (about -269 degrees C). And because no container is perfectly insulated a tank of liquid helium will warm up and boil off in just a few days.

S09E05 - The Perspiration Implementation (Notes and Trivia)

In the opening sequence, Sheldon is wearing a shirt with a transliteration matrix for the comics-version of the Kryptonian alphabet.

Title Reference: The title refers to the machine that Howard invents to make it look like he was exercising.

S09E04 - The 2003 Approximation (Notes and Trivia)

Laura Spencer (Raj's girlfriend Emily) is now promoted to the main cast as her name appears in the opening credits, but is only credited in the episodes she appears in, just like Kevin Sussman as Stuart.

Penny has a hard time containing her laughter with Raj and Howard's song. This was not scripted but Kaley Cuoco breaking character, as can be seen in the blooper reel for season 9, where everyone bursts out in laughter at one point.

The Flash t-shirt Sheldon is wearing after he decided to get back to his lifestyle in 2003 before meeting Leonard is the same t-shirt that he wore when he met Leonard for the first time in the origins episode The Staircase Implementation (2010).

Title Reference: The title refers to Sheldon wanting to return to the unemotional state of his personality before he met Leonard in 2003.

S09E03 - The Bachelor Party Corrosion (Notes and Trivia)

Following her divorce announcement about her husband Ryan Sweeting, Kaley Cuoco's name in the opening credits were reverted to its original billing.

Howard (Simon Helberg) says he learned about the salsa-plus-electricity method, which he uses on the lug nut, from MythBusters (2003). Salsa Escape (2005) of Mythbusters, which aired on 2/23/2005, did, in fact, detail a possible way that a person in jail could have used this method to corrode the bars in his cell to escape.

The recipe for thermite that Sheldon gives is inaccurate, in keeping with standard television practice not to show actual methods of producing dangerous materials.

The van used is the actual van that had been owned by Richard Feynman.

Title Reference: The title refers to the bachelor(ette) parties that corrode and go down hill and the corrosion method applied to the tire lug nut.

When trying to change the tire using percussive shock, Howard and Raj parody Queen's "We Will Rock You", using the words "We Will Percussive Shock You"

S09E02 - The Separation Oscillation (Notes and Trivia)

Melissa Tang, who plays Mandy Chow in this episode, goes on to star as Ms. Fenley in Young Sheldon (2017): Pilot (2017).

S09E01 - The Matrimonial Momentum (Notes and Trivia)

Title Reference: The title refers to how Leonard and Penny's marriage affects the whole gang.

S08E24 - The Commitment Determination (Notes and Trivia)

Raj talks about going with Emily to see the new Avengers movie. This would have been the second Avengers movie, Avengers: Age of Ultron (2015).

Sheldon wonders if he should start watching The Flash. On that show, one of the characters, Cisco, is seen wearing a Bazinga t-shirt in at least one episode.

This is the second episode that doesn't end with laughter, since it ends on a serious note without a punchline. The first one was The Comic Book Store Regeneration (2015).

S08E23 - The Maternal Combustion (Notes and Trivia)

Howard, Raj, and Stuart sing "Hard Knock Life" from the musical Annie (1982) while cleaning the kitchen.

There were plans to have Mary Cooper and Beverly Hofstadter meet as early as season 6, but it didn't happen until this episode because Laurie Metcalf and Christine Baranski weren't available at the same time any sooner.

Title Reference: The title refers to the friction that occurs between Dr. Beverly Hofstadter and Mary Cooper during their mutual visit.

S08E22 - The Graduation Transmission (Notes and Trivia)

Sheldon again mentions the failure of Howard's space toilet, the Wolowitz Zero-Gravity Waste Disposal System seen in The Classified Materials Turbulence (2009). At the time, Howard blamed its failure on a small mistake he made with the diverter valve, but now he claims it was due to "Russian cosmonauts and their potato-based diet".

The on-hold music, "Feels So Good" by Chuck Mangione, is the same tune Sheldon plays on a flugelhorn in his dream in The Relaxation Integration (2017).

S08E21 - The Communication Deterioration (Notes and Trivia)

Title Reference: The title concerns the communication system that Leonard and Raj are developing for NASA to contact aliens and the breakdown of communication between them and the other guys.

S08E20 - The Fortification Implementation (Notes and Trivia)

At the beginning of the episode, Howard and Raj are seen arguing over the pronunciation of GIF. Howard and Leonard argue that it is "gif" because the g stands for graphics, while Raj argues that it is pronounced "jif" because so says the creator of it. In fact, Raj is actually correct in its pronunciation. The creator, Steve Wilhite, has publicly stated multiple times that "jif" is the only acceptable pronunciation. He and his team wanted to pay homage to the Jif peanut butter brand by stating "choosy programmers choose jif", a play on Jif's slogan "choosy moms choose Jif".

S08E19 - The Skywalker Incursion (Notes and Trivia)

In the end scene, Sheldon is wearing a long colorful scarf and jumps through the door of the TARDIS. This long scarf is similar to the one worn by the 4th Doctor from Doctor Who (1963), played by Tom Baker.

On the drive Sheldon expresses concern about a possible hotel detective and Leonard mocks that with a 1930s style comment about hitting the bricks. From the late 1800s to about the 1950s, most large hotels employed house detectives who wandered around looking for thieves, prostitutes, and unmarried couples trying to rent a room together.

Penny is an excellent ping-pong player, as Kaley Cuoco was a nationally ranked child tennis player. The entire cast often plays ping-pong during breaks in rehearsals.

When Sheldon runs away from the guard shack the guard announces a code "AA-23". Princess Leia was held in detention block AA-23 of the Death Star.

S08E18 - The Leftover Thermalization (Notes and Trivia)

Leonard and Sheldon spend most of the episode arguing which is more important, the theory or execution. Sheldon fights for execution and Leonard fights for the idea. Oddly enough, Sheldon is a theoretical physicist and Leonard is an experimental physicist, meaning Sheldon normally is the one with the idea and Leonard normally is the one that executes it.

The part where Bernadette screams to Leonard and Sheldon with the voice of Mrs. Wolowitz is based on the inside joke of the cast that Melissa Rauch does the best impression of her voice. There was even brief talk of Rauch taking over the voice role when original actress Carol Ann Susi passed away, but it was finally decided to have Mrs. Wolowitz pass away in the show as well.

S08E17 - The Colonization Application (Notes and Trivia)

Instead of Mr. Lorre's usual vanity card, the credits end with a tribute to Leonard Nimoy, who died on 27 February, 2015. The tribute reads: "The impact you had on our show and on our lives is everlasting."

One of the rare occasions where we see the wall that the computers and TV sit against. We see it during Sheldon's Mars application video when he throws the pie in Leonard's face.

There actually is a not for profit organization called Mars One. It accepted open applications to anyone in the world interested in being part of a manned expedition to Mars. Their plan is to send an unmanned space craft in 2020 and a manned crew in 2026.

This is the first time we see Leonard wearing glasses with actual lenses in them (when Sheldon throws a pie at him). Previously in every episode he just wore the frames. So did Bernadette and Amy.

Title Reference: The title refers to the application Sheldon is making to become one of the first colonists on Mars.

S08E16 - The Intimacy Acceleration (Notes and Trivia)

In this episode, Sheldon reveals to Penny it's his birthday, a long-held secret from the rest of the friends. In the subsequent spin-off series, Young Sheldon, season 2 episode 2, Sheldon states his birthday is February 26th, the date this episode first aired.

Molly Morgan (Hostess) played 'Bethany,' one of the two Goth girls chatted up by Howard and Raj, in the season 3 episode The Gothowitz Deviation (2009).

Penny say that she was thinking about the day she first met Leonard and Sheldon. Sheldon says it was a Monday afternoon. The first episode aired on September 24 2007, which was a Monday.

The flight number Bernadette gives the baggage attendant, '816' is a reference to the episode the show is on, season 8 episode 16.

The late Dr. David Saltzberg is mentioned as a key character in the escape room that Emily, Raj, Leonard and Amy attend. In reality, Dr. David Saltzberg is the science consultant for the show.

Title Reference: Sheldon and Penny conduct an experiment designed to make people fall in love.

While trying to solve a mystery in the escape room, Amy and Emily are dressed like Velma and Daphne (Scooby-Doo) respectively.

S08E15 - The Comic Book Store Regeneration (Notes and Trivia)

After the cast and crew learned of Carol Ann Susi's death, Johnny Galecki and executive producer Steven Molaro went to the props department and had a commemorative photo of her printed up, which was then afforded a place of honor on Sheldon and Leonard's refrigerator from this episode on, wherein her character passes away as well.

Marks the death of Mrs. Wolowitz, as the actress who provided her voice, Carol Ann Susi, died of cancer on November 11, 2014. On November 11, 2014, it was decided that it would be inappropriate to recast Mrs. Wolowitz and so the character was written out of the show.

The episode won an Emmy Award for Outstanding Multi-Camera Picture Editing for a Comedy Series.

S08E14 - The Troll Manifestation (Notes and Trivia)

Stephen Hawking is revealed to be the internet troll hiding behind the nickname "GeneralRelativity'. Not surprisingly, general relativity was Hawking's main area of expertise.

S08E13 - The Anxiety Optimization (Notes and Trivia)

It is revealed that Sheldon realizes he likes Taylor Swift. When he quotes her by saying "haters gonna hate, hate, hate, hate, hate", he references her song 'Shake It Off'.

Title Reference: Sheldon wants to reach his optimum anxiety level to improve his work performance.

S08E12 - The Space Probe Disintegration (Notes and Trivia)

The Hindu temple seen when Raj takes Howard to visit, is actually the Malibu Hindu Temple, at 1600 Las Virgenes Canyon Road, in Calabasas, CA. (That's about 40 miles West of Pasadena, where the guys live and work.)

Title Reference: Refers to Raj's mental state over the success of a space probe mission he worked on.

S08E11 - The Clean Room Infiltration (Notes and Trivia)

Having made several prior appearances on the show, this is the first time that Brian George as Raj's father appears on screen with the other characters and not via web cam.

Leonard derides Howard's idea to turn off the lights so that the pigeon flies toward the light of the open door. Actually, this is a tried and true method of getting a bird to leave a building into which it has flown and become trapped.

The game that Amy has them play - blowing a ball of wool on a table, with the goal of blowing it off the opponents end - was actually a Victorian era game. Her game 'Hot Boiled Beans' is also from that time, possibly even older.

Title Reference: The refers to the pigeon that Howard let into the clean room they were working in.

S08E10 - The Champagne Reflection (Notes and Trivia)

During the highlights of 'Fun With Flags', the image that appears in between the sections is the apartment flag of Leonard and Sheldon's room (a gold lion rampant on a field of azure).

Professor Sharpe was played by actor Paul Willson who was known for years for sitting on the end of the bar in the sitcom Cheers (1982).

This episode was filmed the day Carol Ann Susi(the voice of Mrs. Wolowitz) was announced to have passed away. Most of the studio audience didn't know due to waiting around outside all day, and the cast did an outstanding job of getting through filming like true professionals. After filming, it was announced to the studio audience and many tears were shed.

Title Reference: When the guys find a bottle of champagne left by a deceased colleague for a never made great discovery, they reflect on their own work and legacies.

When Carol Ann Susi( the voice of Mrs Wolowitz) passed away, they placed a small photo of her on the side of Leonard and Sheldon's refrigerator close to the freezer door. It will stay there for the rest of the series so she is in every episode. This is the first episode you can see it.

S08E09 - The Septum Deviation (Notes and Trivia)

Amy and Sheldon play the 'Heads up' game that Ellen DeGeneres released as an app.

At the hospital Sheldon sits on the right-hand side of the row of seats (from the viewer's point of view) next to Penny. This corresponds to his spot, which he guards so jealously, on his sofa.

In an early scene with Sheldon in Leonard's bedroom, a portrait of Leonard and Penny from the The Prom Equivalency (2014) can be seen on his nightstand.

The normal "Chuck Lorre Productions" card was replaced with a dedication to Carol Ann Susi (Mrs. Wolowitz) who died three days before this episode originally premiered. In reruns, though, the usual Vanity Card is shown.

Title Reference: Leonard goes into the hospital for a deviated septum operation.

When Sheldon and Leonard are discussing the latter's snoring, the photo on Leonard's bedside table is the "prom" photo of Leonard and Penny from the previous episode.

S08E08 - The Prom Equivalency (Notes and Trivia)

Emily says that in the original Cinderella story the two ugly sisters cut off their toes in order to fit the glass slipper. However, if she indeed had read the original (in French), she would know that the shoe wasn't a glass slipper. Instead it was a shoe made out of squirrel fur. It was translated incorrectly initially and the "glass" slipper stuck.

The final episode to feature Carol Ann Susi as the voice of Debbie Wolowitz, who passed away from cancer just one month after this episode was taped, and 5 days after it aired. She could be heard one last time in the ninth season's The Bitcoin Entanglement (2017), where they used an old audio fragment of her.

The scene where Sheldon tells Amy that he loves her was accomplished in one take, making the audience reaction genuine and enthusiastic.

S08E07 - The Misinterpretation Agitation (Notes and Trivia)

Movie memorabilia Items found in Dr. Lorvis' collection include Magneto's helmet from the X-men movies, Hellboy's gun, Indiana Jones' hat and whip, the robots from both Forbidden Planet (1956) and The Day the Earth Stood Still (1951), the Borg Queen's headpiece, Mr. Freeze and Batman suits from Batman & Robin (1997), Maria, the female robot from Metropolis (1927), RoboCop, Terminator, Superman costume, and a Martian from Mars Attacks! (1996).

The voice of Dr. Lorvis' mother was done by Annie O'Donnell, who previously played Amy's mother in the season 4 episode, The Desperation Emanation (2010).

Title Reference: one of Penny's clients misinterprets her flirting, falls for her and every girl that's nice to him, much to Penny's annoyance.

When Amy says the magazine would never consider doing an article on sexy male scientists, Bernadette makes the comment, "Because no one wants to see Neil deGrasse Tyson in a wet t-shirt bend over the hood of a Porsche." Chuck Lorre's title card after the credits of this episode is a photoshopped image of Neil Degrasse Tyson standing by a Porsche in a suit with jacket and shirt open in front to reveal a muscular torso.

S08E06 - The Expedition Approximation (Notes and Trivia)

On the desk in Bernadette and Howard's main room, beside their Wedding photo, is a collectible spacecraft Eagle from the 1970's TV series Space: 1999 (1975).

Title Reference: Since there is an opportunity to study dark matter in a salt mine, Raj and Sheldon decide to test themselves under the conditions found in a mine.

S08E05 - The Focus Attenuation (Notes and Trivia)

At the start of this episode, Sheldon mentions that they never made any progress with their electromagnetic energy idea that they had on 22nd September 2007 because two days later, Penny moved in. The series indeed started on 24th September 2007, opening with Penny moving in in Pilot (2007).

Sheldon again mentions the horror of having watched The Lake House (2006); in The White Asparagus Triangulation (2008), Sheldon complained that Penny made him watch it.

S08E04 - The Hook-Up Reverberation (Notes and Trivia)

The Capitol Comics Store seen in this episode is the same one visited by Stuart and Bernadette in The Occupation Recalibration (2014), although the obnoxious owner Jesse (Josh Peck) is absent this time.

Title Reference: Emily's reaction to Penny, which is the consequence of Penny and Raj having spent the night together three years ago, in The Roommate Transmogrification (2011).

S08E03 - The First Pitch Insufficiency (Notes and Trivia)

it is estimated that the Mars rover would take about 7 minutes to deliver the ball to home plate.

Title Reference: The title refers to the inability of Howard to execute the ceremonial first pitch at a Los Angeles Angels baseball game.

S08E02 - The Junior Professor Solution (Notes and Trivia)

The song that Howard is singing whilst disrupting Sheldon's class is 'All I Do Is Win' by DJ Khaled.

Title Reference: The title refers to Sheldon's new junior professor position at Caltech.

S08E01 - The Locomotion Interruption (Notes and Trivia)

Kevin Sussman (Stuart) once again receives a series' regular credit, after being demoted to guest star for the entire seventh season.

Marks the first appearance of Penny with her new short pixie style haircut. Kaley Cuoco cut her hair between filming of season 7 and 8, and which she makes humorous reference to in the first scene. She officially cut it for a role in the indie movie Burning Bodhi (2015), but later admitted that in reality, she was done with her long hair because of the time needed to style it for the show. By cutting it off, she hoped it would save her time in the makeup chair, but styling her shorter haircut turned out to be even more difficult and time-consuming, making it her worst decision ever.

Taping was delayed by a week due to the contract negotiations of the original five actors, which led to Jim Parsons, Kaley Cuoco and Johnny Galecki earning their first million dollar each.

The story resumes exactly 45 days after the previous episode's events.

Title Reference: The title refers to the interruption of Sheldon's soul-searching train trip.

When Leonard agrees to pick Sheldon up at the Kingman, Arizona, police station and asks him for the address, Sheldon can be heard through Leonard's phone stating that the address is 2730 East Andy Devine Avenue. That is the actual address of the Kingman Police Department. Veteran Western character actor Andy Devine grew up in Kingman, which named that stretch of historic Route 66 after him.

S07E24 - The Status Quo Combustion (Notes and Trivia)

Mrs. Wolowitz's first name, Debbie, is finally revealed.

S07E23 - The Gorilla Dissolution (Notes and Trivia)

The new Spider-Man movie that Sheldon and Raj are trying to see is The Amazing Spider-Man 2 (2014), which was released the week before this episode aired.

Title Reference: Penny's role of the girl/gorilla clone ends after she is fired from the movie.

Wil Wheaton did wind up making a cameo in Sharknado 2: The Second One (2014).

S07E22 - The Proton Transmogrification (Notes and Trivia)

Raj mentions watching Star Wars in the 'Machete Order', which is to start with episode 4 and 5, then proceed with episodes 2 and 3 (as a flashback), and finish with 6. This is a viewing order that some fans have actually advocated to preserve a maximum of surprises, because when watching the films in order of release (4-5-6-1-2-3), Anakin Skywalker/Darth Vader's death already occurs halfway; when watching in chronological order (1-2-3-4-5-6), the twists of Yoda being a Jedi Master and Anakin being Darth Vader as well as Luke Skywalker's father are lost. Leaving out episode 1 is optional, because it doesn't really contain information critical to the overall plot.

The visual effects on this Star Wars-themed episode were created by ILM, the company which did the visual effects on the Star Wars movies. The episode was filmed much earlier than usual and out of sequence, to accommodate Bob Newhart's schedule, and to give ILM time to create the effects.

Title Reference: Professor Proton passes on and "transmogrifies" to a ghost.

S07E21 - The Anything Can Happen Recurrence (Notes and Trivia)

In this episode, the psychic tells Sheldon once he commits to his relationship with Amy, everything will fall into place regarding his work. On the day of Sheldon and Amy's wedding, they come up with Super Asymmetry which goes on to win them the Nobel prize.

Sheldon asks Penny if she ever paid for a meal. In the pilot, she bought the guys food since her ex boyfriend stole their clothes.

Sheldon is considering dark matter as his next field of study. He already did some research on the topic in The Pirate Solution (2009) when he hired Raj to help him with it, although this was mostly done to prevent Raj from being fired and possibly deported.

Title Reference: The revival of "Anything Can Happen Thursday", which was first established in The Hofstadter Isotope (2009).

S07E20 - The Relationship Diremption (Notes and Trivia)

In the first season episode The Jerusalem Duality (2008), Dennis Kim already predicted that string theory was a dead end, and that Sheldon would eventually see it as well. It took Sheldon an additional six years to come to the same conclusion.

One of the fields that Leonard suggests for Sheldon to study is Loop Quantum Gravity. Sheldon once started a fight with Leonard's ex-girlfriend Leslie Winkle (Sara Gilbert) over the superiority of String Theory over Loop Quantum Gravity in The Codpiece Topology (2008), so it is not surprising that he shoots it down immediately.

Title Reference: After advice from Penny, Sheldon starts to treat his giving up of string theory as a diremption (separation or split) between him and his work, like breaking off a personal relationship.

S07E19 - The Indecision Amalgamation (Notes and Trivia)

On the Chuck Lorre Productions, #451 vanity card displayed at the end of the episode, the SERIAL APE-IST 2 script cover page is shown (supposedly written by Vince Gilligan), with a cursive note that appears to say, "Thanks Vince, You're a good sport, bitch! Chuck Lorre". The catchphrase word "Bitch!" was frequently used by the character Jesse Pinkman in Breaking Bad (2008), which was created by Gilligan.

Raj's tale of Altair and Vega is the Chinese legend of Zhinu and Niulang which has been celebrated during the annual Qixi festival for the past 2600 years.

Sheldon mentions that he once made the mistake of going for the Microsoft Zune rather than the Apple iPod, a callback to his line to Raj in The Staircase Implementation (2010): "I assure you, you'll be sorry you wasted your money on an iPod, when Microsoft comes out with theirs." The Zune did mediocre business from the time of release and was discontinued a mere five years afterwards.

Sheldon's red T-shirt shows beakers of chemicals, a plus sign, lightning bolts, an equal sign, and the insignia for The Flash. This equation reflects the comic book origin story of the Flash, where a lightning bolt struck a case full of laboratory chemicals, drenching scientist Barry Allen and endowing him with superhuman speed: Chemicals + lightning bolt = The Flash.

Title Reference: Sheldon, Penny and Raj are all indecisive about choices they have to make.

While Penny and Leonard are reading the script for the movie Penny has been offered, "Ape-Ist 2: Monkey See, Monkey Kill," the front cover of the script is seen, with the screenplay author shown. The name of the screenplay author is Vince Gilligan, who in real life was the writer/producer of both Breaking Bad (2008) and The X-Files (1993).

S07E18 - The Mommy Observation (Notes and Trivia)

At the murder mystery party, the cast is each wearing one of the classic Clue character colors: Raj is Mrs. White (off) white, Penny is Mrs. Peacock blue, Leonard is Miss Scarlet red, Bernadette is Colonel Mustard yellow, Amy is Professor Plum purple, and Stuart is Mr/Rev Green green.

The house we see in this episode used as Sheldon's (Jim Parsons) childhood home is not the house that features in Young Sheldon (2017).

Title Reference: Sheldon sees his mother having sexual relations with a man.

S07E17 - The Friendship Turbulence (Notes and Trivia)

In the opening scene, Sheldon is wearing a t-shirt showing the Sinestro Corps logo from the DC comics.

The table that Leonard and Penny bought in the previous episode is gone in this episode, implying that Sheldon finally got his way and they got rid of it.

This marks the final appearance of Penny's old car. It finally breaks down after Sheldon, Amy and Beverly Hofstadter kept telling her repeatedly that her 'check engine' light was on.

Title Reference: Howard and Sheldon experience some friction in their friendship and they both experience some turbulence while flying on a plane to Houston, Texas.

S07E16 - The Table Polarization (Notes and Trivia)

A MAC computer is always sitting on the desk (although never used) where Leonard wants to place the dining room table. It was removed, and replaced with an older system so Sheldon could go back to Windows 98.

Title Reference: The sides that everyone takes when they discuss getting a dining room table for the apartment.

S07E15 - The Locomotive Manipulation (Notes and Trivia)

Amy's Valentine's Day dinner is on board the Napa Valley Wine Train.

The second time that Leonard and Penny suggest making out on Sheldon's spot on the couch but don't end up doing it. First time was in The Pirate Solution (2009), when Howard interrupted them.

Title reference: Sheldon feels that Amy is tricking him into romance by taking him on a train trip.

S07E14 - The Convention Conundrum (Notes and Trivia)

Carrie Fisher and James Earl Jones, who played Princess Leia and Darth Vader in Star Wars respectively, had never met in real life before this episode, even though they play major characters in the original Star Wars movies. James Earl Jones would always be in a sound booth providing the voice of Darth Vader, and Carrie Fisher would be on set with David Prowse, who provided the physical acting of Darth Vader. This is paralleled in their scene together in this episode where we see Carrie Fisher on-screen , but only hear the voice of James Earl Jones, who is off-screen. The first time they met, Fisher yelled "DAD!" to Jones, a reference to Darth Vader being the father of Princess Leia.

Carrie Fisher lives at number 138, which most likely refers to her character Princess Leia being imprisoned in cell block 1138 in Star Wars: Episode IV - A New Hope (1977). The same number is used as an Easter Egg throughout the Star Wars franchise, and was derived from the title of THX 1138 (1971), a previous movie by director George Lucas.

James Earl Jones came up with the idea of the scene where he rings Carrie Fisher's doorbell and runs away.

Sheldon and Leonard own the limited edition R2-D2 Xbox console. It can be seen in the part where Leonard convinces Raj and Howard to go through with purchasing scalper's tickets.

The names of the possible guests for Sheldon-Con, as seen on his white-board, are as follows: Zachary Quinto, Patrick Stewart, William Shatner, Harrison Ford, George Lucas, Mark Hamill, Matt Smith, Billy Dee Williams, Simon Pegg, Jon Favreau, Ian McKellen, Stan Lee, Andy Serkis, Martin Freeman, Wil Wheaton, Ahmed Best, Robert Downey Jr., Leonard Nimoy, Bill Nye, Carrie Fisher, Adam West, Anybody who played Uncle Ben, Anybody who shot Uncle Ben.

The sushi restaurant Sheldon meets James Earl Jones at is called "Kaiju Sushi". Kaiju means "strange creature" in Japanese, and is also the name of the huge monsters in the movie Pacific Rim (2013). The most famous Kaiju is Godzilla.

S07E13 - The Occupation Recalibration (Notes and Trivia)

Captain Sweatpants' last appearance on the show, and also the only episode in which he has lines.

The rare comic book that Bernadette is trying to replace is "The Dark Knight Returns", the famous Batman story written by Frank Miller.

S07E12 - The Hesitation Ramification (Notes and Trivia)

In the end credits vanity card #436, Chuck Lorre reveals that the filming matches the story where the small part played by a young, relatively unknown actress named Lexie Contursi ended up on the cutting room floor due to no fault of her own. She was supposed to play 'Beautiful Young Woman' who talks to Raj and Stuart, but her scene was cut for time. Lorre stated that he hoped he could give her another role on the show, but unfortunately, this never materialized.

The mall security guard is played by Marcus Folmar. He is the same actor who played the cop that pulls Howard over in Season 10 Episode 1.

The NCIS (2003) episode Penny was supposed to be on was Kill Chain (2014).

S07E11 - The Cooper Extraction (Notes and Trivia)

Amy includes Raj's dog Cinnamon in her connections diagram.

It seems that Kaley had a bit of a cold while filming this episode based on the sound of her voice.

The episode is based on the classic Christmas movie 'It's a Wonderful Life' (1946).

The episode won an Emmy Award for Outstanding Multi-Camera Picture Editing for a Comedy Series.

This is the fourth (out of six) Christmas episode in the series; the others are episodes 2.11 The Bath Item Gift Hypothesis (2008), 3.11 The Maternal Congruence (2009), 6.11 The Santa Simulation (2012), 8.11 The Clean Room Infiltration (2014), and 10.12 The Holiday Summation (2017),

S07E10 - The Discovery Dissipation (Notes and Trivia)

First physical appearance of Ira Flatow on the show. His voice was heard on The Vengeance Formulation (2009) while he was also interviewing Sheldon.

Title Reference: Leonard disproves the existence of the heavy element that Sheldon discovered in The Romance Resonance (2013).

S07E09 - The Thanksgiving Decoupling (Notes and Trivia)

Contrary to popular belief, Jim Parsons did not improvise smacking Mayim Bialik on the backside. Bialik later said that although the smack wasn't in the original script, it was added a few days into rehearsals.

Contrary to the premise of this episode, many wedding chapels in Las Vegas offer pretend wedding ceremonies "for the thrill of a wedding without the lifetime obligation". Even in Las Vegas a wedding license is required for a legal ceremony (available at City Hall from 4 am to midnight), so unless Zach and Penny made the trip downtown to get a license they could very well have gone through a fake wedding ceremony.

The legal definition of "want of understanding" is "the person did not know what a marriage was or understand what was going on" and is one of the most common reasons for annulling a marriage in the state of Nevada. This actually is appropriate for Penny and Zack, as neither one realized the marriage was real.

The mathematics that Leonard and Sheldon do in order to prove to Penny that cow tipping is impossible was previously done by the University of British Columbia. They reached the conclusion that one single person would never have enough strength to tip over a full-grown cow; depending on body type, it would take at least 2 to 4 people to muster enough force to do that, and then only if the cow doesn't adjust its footing or run away. Concerning the latter: cows don't sleep standing up (horses do that). A standing cow at night will be alert and hard to surprise, especially while being approached by 4 people. Even if it doesn't run away, it will shift its weight to prevent from falling over.

The Thanksgiving Day football game Mike and Sheldon discuss (where Mike wanted to shoot his TV and Sheldon's dad did) was the 1993 game between the Dallas Cowboys and the Miami Dolphins. In that game, which was played in a rare snowstorm in Dallas, the Dolphins squibbed their attempt at a game-winning field goal, leaving the ball spinning on the ground with members of the Cowboys surrounding it waiting for it to stop in order to declare it dead. However, Leon Lett ran up to try to grab it, but slipped and inadvertently batted the ball away, which made it a live ball again. The Dolphins recovered, tried the field goal again, and were successful, winning the game.

We come in on Sheldon beer belching Pi and hear the numbers "2,3,8,4,6". That means he had gotten 21 digits into PI.

S07E08 - The Itchy Brain Simulation (Notes and Trivia)

At the end of the episode when Raj is yelling at himself in the mirror you can see a "to victory" Dalek poster from Doctor Who in the reflection on his wall.

Sheldon and Leonard own a "Mythbuster" Adam Savage bobble head doll, which can be seen behind Leonard when he is looking through a junk box.

S07E07 - The Proton Displacement (Notes and Trivia)

Arthur Jeffries tells Leonard that if he'd known people would still be calling him Professor Proton at the age of eighty-three, he would never have given up smoking. Bob Newhart, who plays Dr. Jeffries, was a heavy smoker for years, until he was ordered by doctors to stop in 1985.

Famed children's science show host Bill Nye "The Science Guy" guest stars in this episode. The fictional show "Professor Proton" is loosely based on Nye's show but aired in the 80s when Sheldon and Leonard were children. Bill Nye the Science Guy (1993) aired in the 90s when many millennials were children. Arthur Jeffries, the fictional Professor Proton, accuses Nye of stealing his ideas.

S07E06 - The Romance Resonance (Notes and Trivia)

Bernadette's Song was written by the comedic band Garfunkel & Oates, consisting of Kate Micucci who played Raj's girlfriend Lucy in season 6, and Riki Lindhome, who played Ramona Nowitzki in The Cooper-Nowitzki Theorem (2008).

When Howard and the cast are serenading Bernadette who is in quarantine, the Klingon that Howard speaks in the song is "Heghlu'meH QaQ jajvam" which translates to "Today is a good day to die".

S07E05 - The Workplace Proximity (Notes and Trivia)

Amy's apartment number is 314. The value of Pi is 3.14.

During the argument between Howard and Bernadette, the apartment flag on the refrigerator is seen upside down, indicating that the apartment is in distress.

S07E04 - The Raiders Minimization (Notes and Trivia)

When Amy is telling Sheldon about why Indiana Jones has a 'glaringly obvious' plot flaw, the apartment flag on the fridge is upside down, indicating the apartment is in distress (after Amy tells Sheldon about the plot flaw).

When Raj and Stuart post their internet profiles, the first view on Raj's post is from user "Jenny309". 867-5309/Jenny was a popular hit song in 1982 for Tommy Tutone.

S07E03 - The Scavenger Vortex (Notes and Trivia)

The map coordinate 34.1516,-118.0767 does point to a bowling alley in reality - Bowlmor Pasadena. It is formerly named "300 Pasadena", the name that appeared at the gate of the bowling alley in the show, and the name that Google Maps labels it.

S07E02 - The Deception Verification (Notes and Trivia)

Leonard brings Sheldon a sailor hat, fulfilling a promise mentioned by Sheldon in the previous episode, The Hofstadter Insufficiency (2013).

There is a Bernadette doll in the bookcase behind her in the apartment wearing the same outfit she is wearing in the scene.

Title Reference: The title refers to Sheldon finding out that Leonard has been deceiving him by hiding out at Penny's and not tell him that he was home.

S07E01 - The Hofstadter Insufficiency (Notes and Trivia)

Melissa Rauch went on Conan (2010) and told him an embarrassing story about shooting the episode. During the episode she was supposed to get under the covers of her bed. She told Conan that in real life she likes to hike the sheets up and warm her hands under the covers especially when it is really cold. She did the scene like that once and one of the producers told her that they needed to shoot it again and that she needed to keep her hands outside the blankets because "it looked like she was having too much fun." After they shot the episode a boy came up to her to ask her about it as well.

Sheldon's red T-shirt bears the emblem of Ralph Hinkley's Greatest American Hero costume.

S06E24 - The Bon Voyage Reaction (Notes and Trivia)

Apparently, the dead goldfish found by Sheldon in Penny's closet in The Closet Reconfiguration (2013) belonged to Leonard, but Penny didn't take proper care of it.

First time Raj is able to talk to a non-family member female without drinking alcohol or taking drugs. The writers decided to write his selective mutism out of the series because it became a hindrance in developing stories for Raj, and they felt that all the jokes they could make about it had already been made. Kunal Nayyar and Simon Helberg were also happy that they no longer had to do scenes where Raj has to talk in Howard's ear.

The only episode in the whole series where something besides the end music plays over the end credits. (Raj's incessant talking to the girls from the final scene continues.)

When Sheldon clinks on his glass and says "B-flat for those who don't have perfect pitch", the note produced by him clinking on his glass is indeed a B-flat.

S06E23 - The Love Spell Potential (Notes and Trivia)

Simon Helberg (Howard) really does all those impersonations (Al Pacino, Nicolas Cage, Christopher Walken) himself and has done several others throughout the series. These impressions were specifically set up for Helberg because doing imitations used to be part of his comedy act.

The edition of Dungeons & Dragons that the band is playing is the Fourth. While it had its fans, some players felt that part of the radical innovations introduced by it changed too much the basic nature of the game. After many debates on internet fora (and many players switching to other games), it was superseded in 2014 by the very successful Fifth Edition.

The title refers to the love spell put upon Sheldon and Amy's characters in their Dungeons and Dragons game.

S06E22 - The Proton Resurgence (Notes and Trivia)

The title refers to the return to Sheldon's life of his childhood hero, Professor Proton, who hosted a children's science show. From now on, every episode with the word "Proton" in the title has a guest appearance from Bob Newhart.

This was Bob Newhart's first appearance in what became a recurring role as Professor Proton. Series creator Chuck Lorre had wanted Newhart to appear in one of his shows for years and finally suggested The Big Bang Theory (2007) to him. Newhart agreed, as long as it was a recurring role and the episodes would be taped live.

S06E21 - The Closure Alternative (Notes and Trivia)

Sheldon references the eventual fate of 3 cult TV shows, mentioning that Buffy the Vampire Slayer (1997) "continued on as a comic book", Firefly (2002) did a movie (Serenity (2005)) "to wrap things up", and that Heroes (2006) "gradually lowered the quality season by season till we were grateful it ended."

Sheldon's T-shirt immediately after the opening represents 1950s "The Flash" getting his power. Barry Allen was covered in chemicals (first symbol) after a shelf of them was hit by lightning (second symbol) which resulted in his becoming "The Flash" (third symbol). Thus: Chemicals Plus Lightning Equals the Flash.

The photograph that Raj has on his office wall behind his chair, the one with the two orange rings, is the Hourglass Planetary Nebula taken in 1995 by the Hubble Space Telescope.

The title refers to Amy helping Sheldon work on his compulsion for finishing things or his closure about various activities.

S06E20 - The Tenure Turbulence (Notes and Trivia)

Sheldon and Leonard have the 5 book set of 'Modernist Cuisine' on their fridge. The books explain a new scientific approach to cooking.

S06E19 - The Closet Reconfiguration (Notes and Trivia)

The title refers to Sheldon reorganizing Howard and Bernadette's closet.

S06E18 - The Contractual Obligation Implementation (Notes and Trivia)

Sheldon mentions "professional women using their initials so as not to be prejudged", and names J.K. Rowling and Star Trek's D.C. Fontana as examples. Dorothy Fontana was a very prolific writer on several Star Trek series, but when she began writing for Star Trek (1966), creator Gene Roddenberry indeed advised her to submit screenplays using her initials "D.C.", as networks and studio executives in the 1960s were generally very biased against women writing science-fiction. The real Fontana had actually made a cameo appearance in The Russian Rocket Reaction (2011). Harry Potter author Joanne Rowling was asked by her publisher to use initials, out of fear that the target audience of young boys might be put off by books written by a woman. Even in later years, when Fontana and Rowling became well-known and established writers, they often kept using their better-known initials rather than their full name.

The first appearance of Bert (Brian Posehn), who would later reappear in the season 7 episode The Occupation Recalibration (2014) where he has a crush on Amy.

The girls dress up as Disney princesses. Bernadette is Cinderella, Penny is Sleeping Beauty, and Amy is Snow White.

S06E17 - The Monster Isolation (Notes and Trivia)

Both Raj and his sister Priya attended Cambridge University.

Penny demonstrates her acting skills for the second time, the first being a hemorrhoid commercial in Season 5's The Skank Reflex Analysis (2011).

Penny is the guest on Sheldon's "Fun with Flags" with a show honoring the state flag of Nebraska.

When Sheldon is filming his "Fun with Flags" segment, behind him to his right is the flag of the United States of America. On the other side of the white board is Sheldon and Leonard's apartment flag - Lion rampant on field of azure, as described in Season 3's The Staircase Implementation (2010).

S06E16 - The Tangible Affection Proof (Notes and Trivia)

Alex bought a map of The Canterbury Tales for Amy because it is one of her favorite books. Amy can be heard quoting from this book during the girl's night in The 21-Second Excitation (2010).

First appearance of Kate Micucci as Lucy. Kate is one half of the comedic band Garfunkel & Oates, the other being Riki Lindhome, who played Ramona Nowitzki in Season 2's The Cooper-Nowitzki Theorem (2008). The duo would later write "Bernadette's Song" from The Romance Resonance (2013).

Leonard makes his second marriage proposal to Penny. She abruptly tells him to sit down before he can reveal her last name, assuming he was going to say it.

The girl who played Penny's ex-boyfriend's girlfriend was Kaley Cuoco's younger sister Briana Cuoco.

There is an outtake during the scene when Leonard and Penny are having their argument when they both break character. Prior Penny says that she doesn't have any problems which makes Johnny Galecki state "You don't have any problems, what's your last name?" To which Kaley Cuoco responds with "I don't know."

S06E15 - The Spoiler Alert Segmentation (Notes and Trivia)

As well as being one of the first times there is a glimpse of Howard's mother, it is also the first time she speaks normally without shouting from a distance, when she has just made a meal for Raj.

Penny admits she loves Leonard for the first time without doing it accidentally.

The episode of The Walking Dead (2010) Sheldon is talking about is Season 3's Killer Within (2012).

S06E14 - The Cooper/Kripke Inversion (Notes and Trivia)

Sheldon listens to the Imperial March from the Star Wars saga and wears an afghan reminiscent of the Emperor's cloak.

The "scale replicas" received by Howard and Raj actually have each other's haircuts.

S06E13 - The Bakersfield Expedition (Notes and Trivia)

Howard's Borg costume is specifically from Star Trek: The Next Generation (1987). Budget restrictions on Next Generation forced the makers to settle for that particular design. When the Borg re-appeared in Star Trek: First Contact (1996) and Star Trek: Voyager (1995), the bigger budget allowed for a more elaborate re-design.

In this episode, we learn another animal Sheldon does not like: hamsters.

The comic Stuart presents as a suggestion to the girls, "Fables #1", is a real comic. It's actually called, "Fables Vol. 1: Legends in Exile". The artwork on the cover is the original artwork of the issue. Other reissuings have different artwork, making the original a collectors item.

The four state capitals not served by the interstate highway system are: Juneau, AK; Dover, DE; Jefferson City, MO; and Pierre, SD.

The label on the GPS in the car reads "AGELLA", which is "MAGELLAN" with the first and last letters removed.

S06E12 - The Egg Salad Equivalency (Notes and Trivia)

First appearance of Janine Davis from Human Resources (Regina King).

S06E11 - The Santa Simulation (Notes and Trivia)

Bernadette's working uniform is shown again. On the left chest there is a blue "ZANGEN" sign in an ellipse.

Leonard recounts his early Christmas experiences where he had to leave Santa Claus a research paper, which would then be graded. This is consistent with his account in The Maternal Congruence (2009), where during Christmas, everybody had to write research papers on the anthropological and psychological implications on human society, after which they broke off into focus groups and critiqued each other.

The Jingle Bells bells are in no noticeable order among the participants. Left to right: Howard plays 2 & 1; Stuart plays 3 & 6; and Sheldon plays 5 & 4 (i.e. stage right to stage left).

S06E10 - The Fish Guts Displacement (Notes and Trivia)

First and last appearance of Meagen Fay as Bernadette's mother. Mrs. Rostenkowski was first seen from above in The Countdown Reflection (2012), but she wore a big hat and was played by an uncredited extra.

The game that the guys are playing in the opening scene is Ticket to Ride.

The scene in which Sheldon spanks Amy, Jim Parsons and Mayim Bialik both had a very difficult time staying in character, and several takes were ruined with them bursting out in laughter.

The scene where Penny was teaching the guys about fishing has her being the "manliest" in the demonstration. However, off-camera it was entirely the other way around. Kaley Cuoco was the grossed out one while the guys were way less so. Accordingly, between takes they held up a worm and chased her around the set while she was running and screaming.

S06E09 - The Parking Spot Escalation (Notes and Trivia)

During Bernadette and Amy's initial argument, when Penny says, "Damn!", it wasn't scripted.

Sheldon's explanation of why he prefers his old parking spot (it is a corner spot that reduces the risk of door-dings in half, it's very close to the building entrance, a nearby tree provides shade on hot days and is also home to a delightful squirrel) is analogous to his explanation of why he prefers his spot on the couch from Pilot (2007) (In the winter it's close enough to the radiator to remain warm but not cause perspiration, in the summer it's directly in the path of a cross breeze from the windows, it faces the television at an angle that is neither direct, thus discouraging conversation, nor so far wide to create a parallax distortion).

Sheldon's parking spot is #294. The two campus buildings adjacent to parking spot 294 are the Loeb Building and the Bendis Building.

While discussing the nature of vampires, mummies, and zombies, Raj mentions zompires which are creatures recently introduced in Buffy the Vampire Slayer season 9 comic.

S06E08 - The 43 Peculiarity (Notes and Trivia)

Howard says that it took Sheldon two years to finish a Lego Death Star. Sheldon could be seen working on it in The Isolation Permutation (2011).

The show's most-watched episode ever in the US, with 17.4 million viewers.

This is the first time that Penny actually tells Leonard that she loves him, though admittedly it was accidentally. A somewhat reverse situation happened in Season 3's The Wheaton Recurrence (2010) when Leonard says it to Penny, and she responds, "thank you."

This is the last episode to just feature the 5 original cast members.

S06E07 - The Habitation Configuration (Notes and Trivia)

In the opening scene, Wil Wheaton is wearing The Guild (2007) shirt. Up until the previous year, he had been playing a recurring role in that series.

This is the first time in any of Wil Wheaton's appearances that the audience makes any kind of reaction when he is first seen.

When Sheldon goes to Wil Wheaton's home, his house number (1701) is visible. 1701 is the number in the registry for the U.S.S. Enterprise-D (NCC-1701-D) in Star Trek: The Next Generation (1987) in which Wheaton appeared.

S06E06 - The Extract Obliteration (Notes and Trivia)

Kunal Nayyar again displays his ear for accents when he perfectly mimics an American accent while discussing prank calling call centers in India.

Sheldon reports that his mother always says "To thine own self be true." She is, in fact, quoting Polonius in Act 1, Scene 3 of Shakespeare's play Hamlet.

S06E05 - The Holographic Excitation (Notes and Trivia)

Besides the above mentioned couples costume ideas, the ones listed on Sheldon's side are R2-D2 and C-3PO, Hewlett & Packard, Batman & Robin, Jobs & Wozniak, Kirk & Spock, Arthur Dent & Ford Prefect, and Doctor Who & a Dalek. The ones on Amy's side (besides those mentioned above), are Cinderella & Prince Charming, Anthony & Cleopatra, Lady & Tramp, Romeo & Juliet, Jack & Rose from Titanic (1997), and Dharma & Greg (a show also produced by Chuck Lorre). Also mentioned in dialog: Sheldon suggests salt and pepper (the condiments, not the rappers), and Amy offers Raggedy Ann and Andy.

Buzz Aldrin, the second man to walk on the moon after Neil Armstrong, makes his first guest appearance on the show.

Howard makes a point of how everyone's tired of him bragging about being in space by doing a perfect imitation of Bernadette, to which she responds (in a lower tone than usual) "I don't sound like that." Melissa Rauch uses her actual voice when saying this line.

Leonard and Penny's tryst inside the TARDIS is an inside joke. It parodies the honeymoon of the Doctor's companions Amy Pond and Rory Williams in Doctor Who (2005), which took place inside the TARDIS and is a major plot point of the sixth season. In addition, Penny wears a sexy Policewoman's outfit, parodying Amy's job as a kiss-o-gram girl in a similar costume.

The purple witch at the comic store party, Janelle Marra, had previously appeared with Kaley Cuoco in the Charmed (1998) episode Repo Manor (2006). In the Charmed episode however, Cuoco played a witch who vanquished Marra's demon.

S06E04 - The Re-Entry Minimization (Notes and Trivia)

During the pie eating contest scene, as Amy (Mayim Bialik) is counting down, Penny (Kaley Cuoco) looks directly into the camera with a clearly uncomfortable expression just moments before putting her face into the blueberry pie.

In the opening teaser, when Stuart says he can give Sheldon 30% off comics, you can see Jim Parsons smile and break character.

Sheldon is wearing a "73" shirt. In season 4, he mentions that 73 is the best number. Coincidentally, Jim Parsons was born in 1973.

This is the third time in which Mayim Bialik's broken right hand from a real-life accident had to be hidden. When Penny is taunting Sheldon about losing Pictionary and Leonard points out it's a well-rounded game, Amy can be seen placing the box on the table, revealing her right hand laying weirdly dead on the couch, one finger is jarred in a way that makes it look like it's made of rubber.

S06E02 - The Decoupling Fluctuation (Notes and Trivia)

Mayim Bialik was in a car accident between the filming of The Date Night Variable (2012) and this episode. She sustained a serious injury on her right hand, and for a short while there was a possibility that she might lose some fingers. Fortunately, that wasn't the case, but she had to wear a cast on her right arm for several weeks. For several episodes starting with this one, Mayim's right hand had to be kept out of each shot, just like with Kaley Cuoco's broken leg after a horse riding accident in the fourth season.

Michael Massimino said in a supplementary featurette for the Season 6 DVD box set that any real teasing and pranking of another astronaut while in orbit would not have been mean-spirited due to the long training they would already have undergone together and the close quarters of the spacecraft and station necessitating good working relationships. He even recounted how he risked getting the nickname "Crybaby" over how he teared up while looking at Earth during a spacewalk, which could have shorted out something in his helmet and provoke an investigation in which he'd would have to admit to crying.

Sheldon tells Penny that Higgs was on track for winning the Nobel. On December 10, 2013 Higgs was awarded the Nobel prize in physics for the Higgs boson discovery.

The episode won an Emmy Award for Outstanding Technical Direction, Camerawork, Video Control for a Series.

S06E01 - The Date Night Variable (Notes and Trivia)

The music Stuart plays at the end is "Desafinado" as performed by Stan Getz.

The scenes of Howard in space were accomplished by filming in a Space Station replica in Canoga Park, California. Only 20 feet of station were available, so over the course of this episode and the next, creative camera angles and framing made it look like there were many different sections. Weightlessness was created by supporting the actors on a very thin platform and have them simulate the effects of microgravity.

While Howard (Simon Helberg) is video chatting with Bernadette (Melissa Rauch) from the International Space Station, the clipboard next to the computer can briefly and clearly be seen, twice, with a letter clipped on top. The address section of the letter is to Varese Saraband Records, best known in Hollywood as a prime record label specializing in film scores, soundtracks, and original cast recordings.

S05E24 - The Countdown Reflection (Notes and Trivia)

The wedding was held on the roof of the Madison Luxury Apartments at 215 S. Madison St. in Pasadena.

S05E23 - The Launch Acceleration (Notes and Trivia)

The gas Leonard brings to Penny is Sulfur Hexafluoride. It is 6 times denser than air, thus causing the 'Darth Vader' voice. It is an inert gas and safe to breathe in small quantities.

S05E22 - The Stag Convergence (Notes and Trivia)

Penny calls the guys the Lost Boys, a reference to the characters in J.M. Barrie's famous work, Peter Pan (1960).

When Leonard says that he is going to have sex with Penny in the laundry room, the sign that normally says "Please keep your clothes on while doing laundry" is conveniently obscured by detergent bottles.

S05E21 - The Hawking Excitation (Notes and Trivia)

Jim Parsons revealed that the writers originally wanted him to enter the university restaurant while wearing a metal bikini like Princess Leia in Star Wars: Episode VI - Return of the Jedi (1983). He said that he would only do it if they gave him six months and a personal trainer, so they conceived of the French maid costume instead.

Stephen Hawking's original singularity theorems from the 1960s and '70s were written up on the whiteboards on set.

S05E20 - The Transporter Malfunction (Notes and Trivia)

Amy is not in this episode because Mayim Bialik was on a tour to promote her new book at the time.

This is the first time that Leonard Nimoy has been cast in the series. The producers of the show have been trying for many years to get Nimoy to appear on the show, which was difficult due to him having mostly retired from acting.

When Sheldon dreams that he's woken up on an alien planet, the distinctive arch of the Guardian of Forever from the original Star Trek (1966) series episode The City on the Edge of Forever (1967) is visible in the background.

S05E19 - The Weekend Vortex (Notes and Trivia)

For some reason, Kaley Cuoco is omitted from the credits, despite appearing in the episode.

It is revealed that Amy is from Glendale.

S05E18 - The Werewolf Transformation (Notes and Trivia)

At one point while talking to Bernadette about astronaut training, Wolowitz makes a reference about attending sunset Sabbath services at "Camp Hess Kramer". This is a real camp operated by Wilshire Boulevard Temple in Los Angeles and has been in existence since the fifties.

Howard experiences zero gravity in an airplane that flies straight up into the air and then straight back down. He says he threw up during the experience. For this reason, astronauts lightheartedly call this airplane "The Vomit Comet."

Sheldon claims his hair grows at 4.6 yoctometers/femtosecond. That converts to 1.2 cm in 30 days which is consistent with normal hair growth rates.

The strip on the back of Jim Parsons's head was shaved bald for real. The show was on a brief hiatus afterwards, so there was enough time to have Parsons grow it back.

When Leonard mentions changing reality by going back in time and killing a bug, he is referring to a short story "A Sound of Thunder" by Ray Bradbury about a sportsman going back in time to shoot an already doomed Tyrannosaurus rex and steps off the designated path, kills a butterfly changing the history/reality of his time.

S05E17 - The Rothman Disintegration (Notes and Trivia)

None of the guys share any scenes with the girls in this episode.

Sheldon explains the rules of Rock-Paper-Scissors-Lizard-Spock twice. In both cases, he uses exactly the same words in the same order together with identical hand gestures. They are also exactly the same as when he explained the rules in The Lizard-Spock Expansion (2008).

When Sheldon is complaining about his new office you can see on the white board that he has written the notes the chimes play and several combinations of notes the bird sings.

While the set dressing in the bathroom scene at the university may look normal at first, the mirrors mounted on the back wall over the sinks are actually tilted downwards at a slight angle so they only reflect the bathroom floor. This was done to prevent them from reflecting the cameras & studio audience in them, which they would do if they were mounted properly.

S05E16 - The Vacation Solution (Notes and Trivia)

Leonard sings "I gotta feeling" by Black Eyed Peas in his car.

Sheldon claims Einstein failed math. This common belief is completely false. Einstein was doing differential calculus before the age of 10. Granted, he once said he could have taken his work further but he lacked the math; however, no other physicist had the math at that time.

S05E15 - The Friendship Contraction (Notes and Trivia)

Michael Massimino, a NASA astronaut, makes a cameo appearance.

Open the pod bay doors, Hal is a reference to the movie 2001: A Space Odyssey (1968).

S05E14 - The Beta Test Initiation (Notes and Trivia)

Becky O'Donohue provides the voice of Siri, and portrays her as an actual woman in Raj's nightmare.

During his reseach on flag information for his show "Fun with Flags", Sheldon finds out that during the 1936 Summer Olympics, Liechtenstein did come to the realization that its flag was identical to the flag of Haiti. Because of this finding, the government added the prince's crown to the canton. This change served two purposes, to signify Liechtenstein's position as a principality, and to "distinguish" its flag from Haiti's. This modified design was adopted on June 24, 1937.

The flag on the right side of Sheldon and Amy's video is the apartment flag that Sheldon had made and is first seen in The Staircase Implementation (2010).

S05E13 - The Recombination Hypothesis (Notes and Trivia)

The game featured in this episode, "Settlers of Catan", is a real game, and the concept of "wood for sheep" has been a running joke among regular players of the game since its inception.

This episode marks the 100th episode of the show, which began airing on September 24 2007, with the pilot episode.

When Leonard first sees Penny she is framed in the doorway of her apartment and dressed in the same clothes, blue shirt with a pink floral design, as the way Leonard first saw her in the series pilot. Leonard and Sheldon are also dressed in a similar fashion.

S05E12 - The Shiny Trinket Maneuver (Notes and Trivia)

The tiara that Sheldon gives Amy is worn by Amy when they go to Copenhagen in the last episode to get their Nobel Prize.

S05E11 - The Speckerman Recurrence (Notes and Trivia)

As a weird thing mentioned by Sheldon, The Harlem Globetrotters did visit Pope John Paul II at the Vatican in November 2000 and named the Pontiff an Honorary Harlem Globetrotter.

Lance Barber, who plays Leonard's bully Jimmy Speckerman, would later go on to play Sheldon's father, George, on the show Young Sheldon (2017). He also appears as George Cooper Sr. in season 12's The VCR Illumination (2018) via a video cassette tape recording.

Sheldon is watching Saul Perlmutter receiving his Nobel Prize live on television. The episode was indeed broadcast on 8th December 2011, the same day that Perlmutter did receive the Nobel Prize.

S05E10 - The Flaming Spittoon Acquisition (Notes and Trivia)

First appearance of Sheldon and Amy's Relationship Agreement. There are 31 pages in it, and among its many clauses are sections describing situations in which hand-holding is permitted, and responsibilities in case of injuries ("Booboos and ouchies").

One of the t-shirts Sheldon wears shows the image of Green Lantern, Vol. 2, #90, from September 1976, one of the famous Neal Adams/Denny O'Neill collaborations.

Stuart's last name is Bloom, as seen on his Facebook page.

The Mystic Warlords of Ka'a card game was created by the art department, with the cards mentioned in this episode being never been mentioned before. This is a running joke throughout the series, mocking the ridiculous complexity of the game, but this is the first time the characters start to realize this.

S05E09 - The Ornithophobia Diffusion (Notes and Trivia)

Lovey Dovey is a Black-throated Magpie Jay

Penny tries to humiliate Leonard in front of another woman by revealing that he has not one but two Star Trek uniforms. In The Prestidigitation Approximation (2011), we learned that he has an everyday uniform and a dress uniform.

Sheldon's encounter with an angry chicken that once chased him into a tree was mentioned before in The Jiminy Conjecture (2009) and The Cruciferous Vegetable Amplification (2010).

The helmet that Sheldon puts on to scare away the bird is from the character Boba Fett, the infamous bounty hunter from the Star Wars universe.

S05E08 - The Isolation Permutation (Notes and Trivia)

Amy's apartment door number is 314. This is the same number as Pi (3.14), and Albert Einstein's birthday (March 14).

S05E07 - The Good Guy Fluctuation (Notes and Trivia)

Final appearance of Priya Koothrappali (Aarti Mann) in the series. The next episode confirms that Leonard is single again and that he and Priya broke up.

The mask Leonard uses to frighten Sheldon is a mask of the Star Trek (original series) character "Balok" from the The Corbomite Maneuver (1966).

The sketch that Leonard claims was drawn by Jim Lee was in fact drawn by the famous comic book artist at the show's request.

S05E06 - The Rhinitis Revelation (Notes and Trivia)

Mary confirms that Sheldon was tested for insanity as a child and the doctor said he was fine. She does regret, however, about not taking him to a follow-up specialist in Houston.

Sheldon's oft-repeated habit of offering a hot beverage to a distressed house guest is apparently something that his mother taught him.

When Sheldon returns to the apartment after getting caught in a downpour, the tissue box Leonard offers him is inside a cover made to resemble the design of a Rubik's Cube. This item is seen as a background prop in many episodes.

S05E04 - The Wiggly Finger Catalyst (Notes and Trivia)

At Wil Wheaton's party, two of the background guests are played by D.C. Fontana, writer for Star Trek (1966), Star Trek: The Next Generation (1987) and Star Trek: Deep Space Nine (1993); and David Gerrold, writer for the same series and Star Trek: The Animated Series (1973). They are the two people seen talking to Stuart when Sheldon enters.

Penny is wearing a Captain America t-shirt towards the end of this episode.

The poster on the wall in Wil Wheaton's house is a signed copy of a Stand by Me (1986) poster.

The sword that is featured in the opening shot was an actual sword from Game of Thrones (2011). It was valued at $10,000 and Johnny Galecki was reluctant to wield it.

Where most episodes take place over a few days, this one takes place over a month, as mentioned by Raj, and illustrated by how Sheldon managed to grow a mustache and Raj to learn sign language.

S05E02 - The Infestation Hypothesis (Notes and Trivia)

Sheldon proposes a riddle to his friends which is to get the four-letter word which means both a printer's type and a compulsion to eat dirt. The answer is "pica".

When Penny greets Sheldon at the door with the phrase, "What's the word, hummingbird?", she is repeating a line from the song "The Telephone Hour" from the musical Bye Bye Birdie (1963).

S05E01 - The Skank Reflex Analysis (Notes and Trivia)

Beverly's appearance was on a Skype screen since Christine Baranski was filming another series in New York.

S04E24 - The Roommate Transmogrification (Notes and Trivia)

After the end of this season, the series was renewed for three more seasons. It marked the first time a TV series was renewed for more than one season at a time.

When Sheldon mentions "an eye for an eye" from the Hammurabi Code, he is not quoting the Bible (although the phrase does appear in St. Matthew's Gospel) but the legal code of King Hammurabi, ruler of Babylon in the first half of the eighteenth century B.C.

S04E23 - The Engagement Reaction (Notes and Trivia)

The Mystic Warlords of Ka'a card game was created by the art department and appears in a number of episodes: The Justice League Recombination (2010), The Engagement Reaction (2011), The Flaming Spittoon Acquisition (2011), and The Decoupling Fluctuation (2012)).

When Howard is talking to his mother about Bernadette while she is in the washroom, the pictures seen on the wall of Howard as a kid are real pictures of Simon Helberg as a child.

S04E22 - The Wildebeest Implementation (Notes and Trivia)

During the coffee shop scene, after Raj takes off his underwear, Sheldon can be seen smiling/smirking which is why he has his finger over his mouth at that moment.

There are in fact several three-player chess variants. The type Sheldon designed has custom pieces (the Old Woman, the Grand Empress). These types of custom pieces are called "fairy-pieces" by chess aficionados.

S04E21 - The Agreement Dissection (Notes and Trivia)

After kissing Amy for the first time, Sheldon says "fascinating." This is the catchphrase of his idol, Spock from Star Trek (1966).

The code Sheldon uses to activate the "self destruct" sequence on his laptop, 1-1-A-2-B, is the code used by Spock in Star Trek (1966): Let That Be Your Last Battlefield (1969). The layout of the program he is using for the countdown is similar to the designs of the computer screens seen first in Star Trek: The Next Generation (1987).

The waltz that Sheldon la-la's to the taxi driver is The Blue Danube Waltz by Johann Strauss the Younger.

S04E20 - The Herb Garden Germination (Notes and Trivia)

While playing Wii Sports archery, Sheldon is wearing purple and blue. These are the colors of the comic book version of the Avengers' resident archer Hawkeye.

S04E19 - The Zarnecki Incursion (Notes and Trivia)

In the opening scene, in which Sheldon discovers his account has been hacked, he says "It is time to cry havoc and let slip the dogs of war!" He's quoting Marcus Antonius in Shakespeare's Julius Caesar, who is preparing to strike back at Caesar's assassins, but he is more likely referring to the Klingon General Chang in Star Trek VI: The Undiscovered Country (1991) who used the same line.

Raj says that they are getting offered help on the internet from a "member or the Nigerian royal family". This refers to the infamous 'Nigerian Prince' phishing emails that have often been used since the early 2000s to cheat people out of money. The scam usually involved a person claiming to be the beneficiary of a large sum of money from a will, but needing a deposit to obtain it, and promising to share the fortune if the receiver of the email sends over the deposit.

The 'bat'leth' that Sheldon brings to the bully's house is a typical Klingon weapon.

The name Zarnecki is a tribute to Professor John Zarnecki who was the lead scientist on the Cassini/Huygens mission to Saturn's moon Titan.

This is the only time where you can see what car Leonard Drives. When they break down on the highway you can see that it is a 2007 Saab 9-3 Aero.

S04E18 - The Prestidigitation Approximation (Notes and Trivia)

The technique Raj uses to shuffle the cards is called a Hindu Shuffle.

S04E17 - The Toast Derivation (Notes and Trivia)

LeVar Burton makes the fifth person from Star Trek franchise to be on the show. The others are George Takei, Wil Wheaton, Brian George, and Mark Harelik.

The line "The horror" was referencing the film Apocalypse Now (1979). The line was also used in a similar fashion in The Dead Hooker Juxtaposition (2009).

S04E15 - The Benefactor Factor (Notes and Trivia)

When Sheldon says, "Oh, the humanities!", it is a play on Herb Morrison's 1937 radio account of the destruction of the airship Hindenburg. Part of Morrison's report included the phrase, "Oh, the humanity!"

S04E14 - The Thespian Catalyst (Notes and Trivia)

When Sheldon is doing improv with Penny, he says he sees a sign that reads "Camarillo State Mental Hospital". While this was an actual hospital, it closed in 1997, and this episode was aired in February 2011. The hospital has since been redeveloped and is now California State University Channel Islands.

S04E13 - The Love Car Displacement (Notes and Trivia)

This episode marks the first time Howard uses the nickname "Bernie" for Bernadette.

When Sheldon calls Howard in the car with the words "Red Leader to Red Five" he is imitating one of the X-Wing pilots in the film Star Wars: Episode IV - A New Hope (1977). Red Five was Luke Skywalker's X-Wing call-sign in the movie.

S04E12 - The Bus Pants Utilization (Notes and Trivia)

Jim Parsons learned how to play the theremin especially for this episode. The first melody that Sheldon tries to play on his theremin after saying how much he loved the use of this instrument in the opening tune of Star Trek (1966) is, in fact, said opening tune. It should be noted though that the theremin wasn't actually used in it; what sounds like a theremin was actually a soprano vocalizing.

S04E11 - The Justice League Recombination (Notes and Trivia)

At the end of the episode, when Sheldon runs to the Grand Canyon, the song playing is The Flight of the Bumblebee " which is the theme song of another hero, The Green Hornet (1966).

Our friend the beaver was the title of Zonker Harris's college-level biology term paper in the comic strip Doonesbury.

Stuart's costume is Tom Baker's version of Doctor Who (1963) aka Doctor #4.

S04E10 - The Alien Parasite Hypothesis (Notes and Trivia)

Amy tells Zack that she wants to grab hold of his gluteus maximus and make Shakespeare's metaphorical beast with two backs. She is telling him that she wants to grab his backside (the gluteus maximus is the main muscle in the buttock) and have sex with him. The "beast with two backs" is a quotation from Shakespeare's Othello (Act 1, Scene 1).

Amy's and Sheldon's dialogue during the differential diagnosis is reminiscent of the classic Abbott & Costello comedy routine "Who's on First?"

As a solution to Amy's problem, Sheldon mentions the Vulcan technique of 'Kolinahr' from Star Trek: The Motion Picture (1979), where Vulcans learn to repress all their emotions including sexual desire (though he neglects to mention that even Vulcans go through a process called 'pon farr' every seven years, where they experience an overpowering drive to mate). After Amy tells Zack that she will try Kolinahr, Sheldon gives Zack the Vulcan hand greeting.

Not only is the number 73 important marking the year actor Jim Parsons was born, this is also the 73rd episode of the show.

Raj's guess of 5,318,008 for the "best number" spells "BOOBIES" if you type it into a calculator and turn it upside down.

The whiteboard behind Sheldon as he tries to do a differential diagnosis on Amy's symptoms shows a schematic for the metabolism of glucose.

While Sheldon and Penny are talking in the laundry room, there's a sign behind Penny on the wall that reads: "Please Keep Your Clothes On While Doing Laundry"

S04E09 - The Boyfriend Complexity (Notes and Trivia)

Bernadette says that Howard constantly uses the joke that his fortune cookie says, "Help. I am a prisoner is a fortune cookie factory." Simon Helberg, who plays Howard, used the same joke in an extra included on the Season 3 DVD of the show where the actors cracked open fortune cookies to read questions to each other.

One of the computer screens in the telescope lab shows the user name "saltzberg". David Saltzberg is the show's science consultant.

The piece of paper that clings to Sheldon's head immediately after throwing the Penny-specific Roommate Agreement section in the air was completely unintentional. Jim Parsons and Johnny Galecki can be seen on the DVD set's gag reel smiling at this happening; they completed the scene, and the part where they broke character was edited out.

This marks the first episode where Bernadette imitates Mrs. Wolowitz.

When Raj mentions "Our babies will be smart and beautiful" to make fun of Leonard about him and Penny. This is an obvious callback to the pilot when after Penny goes back to her apartment he says the same thing.

S04E08 - The 21-Second Excitation (Notes and Trivia)

Because of her broken leg Kaley Cuoco is shown working as The Cheesecake Factory's bartender again, instead of her normal job as a waitress. Also, a body double is used when Penny storms off near the end of the show.

First episode in which Mayim Bialik and Melissa Rauch's names are shown in the beginning of the episode with the rest of the main cast.

Penny tells Leonard she can't believe he's never read Eat, Pray, Love by Elizabeth Gilbert. Raj says the book changed his life and later tries to tell the guys about it. Eventually, Leonard can be seen reading it while the guys are waiting in line to get into the movie theater.

The ending of the episode where Sheldon runs from the theater is a spoof of the opening scene of Raiders of the Lost Ark (1981).

The Miller's Tale from Geoffrey Chaucer's "Canterbury Tales" really is filthy. At the denouement a wife is having sex with her lover when she sticks her rear out a window to trick a nerdy cleric into kissing her lower lips but he gets suspicious because he knows a woman has not a beard so he gets a red hot poker and shoves it up the ass of the wife's lover who yells for water causing the cuckolded husband to cut a rope suspending himself from the barn roof causing him to fall and break a few bones. Amy's recount, while properly using some Old English words, is clearly a condensed/unexpurgated version.

The quote that Sheldon uses against Wil Wheaton comes from Jean-Luc Picard fighting the Borg invasion in Star Trek: First Contact (1996). Wheaton played Wesley Crusher in Star Trek: The Next Generation (1987) where Picard was his captain, but was absent from First Contact.

The so-called "submarine controversy" from Raiders of the Lost Ark (1981) refers to the scene where Indiana Jones grabs hold to the outside of a Nazi submarine and rides it all the way to their hidden island base. The "controversy" is how Indy knew the sub wouldn't submerge and likely cause him to drown. In novelizations and comic adaptations of the film, the submarine does submerge, but Indy lashes himself to the periscope, which remains above water.

The yelp that Kaley Cuoco blurts out when Mayim Bialik hits her with a pillow was genuine, as she wasn't expecting to actually be hit with it.

This is the first episode the girls all share a scene together.

Two of the men accompanying Wil Wheaton to the movie are Captain Sweatpants and Lonely Larry, who are frequently seen in the Comic Book Store; the third man (Jesse Heiman) was first introduced in The Desperation Emanation (2010) as a Comic Book Store customer. He makes three more appearances in the show (at Wil Wheaton's party in The Russian Rocket Reaction (2011); at Howard's stag party in The Stag Convergence (2012), and during the Valentine party in The Tangible Affection Proof (2013)) but never received a nickname.

S04E07 - The Apology Insufficiency (Notes and Trivia)

Howard's middle name, Joel, is revealed in this episode.

Kaley Cuoco appears in two scenes: in one, she is filmed standing behind the bar at the Cheesecake Factory, and in the second, she sits in the gang's living room behind a table. This was to hide her broken leg due to a horseback riding accident.

This is the second time that Penny tries to get rid of a customer at the Cheesecake Factory by suggesting they go to the Olive Garden instead, after The Cruciferous Vegetable Amplification (2010).

S04E06 - The Irish Pub Formulation (Notes and Trivia)

Lucky Baldwin's, the Irish pub that Sheldon references, is actually a real pub located in Pasadena, CA. The address is 17 S Raymond Ave, Pasadena, CA 91105.

Raj refers to Priya as his "baby sister" when announcing her visit. Aarti Mann, who plays Priya, is actually three years older than Kunal Nayyar, who plays Raj.

Sheldon references a Bob's Big Boy in Toluca Lake. There actually is a Bob's Big Boy at 4211 West Riverside Drive in the Toluca Lake (Burbank) area of California.

The only episode where none of the 3 main women (Amy, Penny and Bernadette) appear.

This episode and the previous one, The Desperation Emanation (2010), are the only episodes in which Penny doesn't appear, due to Kaley Cuoco's horseback riding accident where she broke her leg.

S04E05 - The Desperation Emanation (Notes and Trivia)

Due to a horseback riding accident where she broke one of her legs, Kaley Cuoco is absent from this episode and the next, and is listed as credit-only.

Marks the first time Amy Farrah Fowler's mother is seen, and the only time she is played by Annie O'Donnell before being re-cast with Kathy Bates in season 11.

Title reference: Amy claims that Leonard wants a girlfriend so badly that he is literally emanating pheromones that make him stink of desperation.

S04E04 - The Hot Troll Deviation (Notes and Trivia)

No scenes occurred in Leonard and Sheldon's apartment.

Sheldon describes Raj's desk as a "brobdingnagian monstrosity", explaining that it is a British idiom. He's referring to the imaginary giants' kingdom of Brobdingnag in Jonathan's Swift's book "Gulliver's Travels". Brobdingnagian means excessively large.

The costume George Takei is wearing is the same costume he wears in Star Trek IV: The Voyage Home (1986).

The scene when Howard is "alone" with himself in his bedroom features the theme music from A Man and a Woman (1966), by French composer Francis Lai, who is possibly most famous as being the composer of the theme to the film Love Story (1970). It is performed by the piano duo of Art Ferrante and Lou Teicher.

S04E03 - The Zazzy Substitution (Notes and Trivia)

Jim Parsons has revealed in an interview that he, much like Sheldon, is allergic to cats.

The title refers to the cat named Zazzles (whom Sheldon thinks is Zazzy) that he gets to replace Amy in his life after they break up.

S04E02 - The Cruciferous Vegetable Amplification (Notes and Trivia)

One of three episodes where Sheldon (Jim Parsons) wears shorts; the others are The Luminous Fish Effect (2007) and The Rothman Disintegration (2012)

The song played by Sheldon in the car is Greensleeves.

The woman seated with Steve Wozniak, Janet Hill, is Steve's wife in real life. They have been married since 2008.

There are multiple The Wizard of Oz (1939) references in this episode. First, when Sheldon says don't pay attention to the man laying in the bed. Second, when they call Steve Wozniak the great and powerful Woz.

S04E01 - The Robotic Manipulation (Notes and Trivia)

According to Mayim Bialik, Amy wasn't conceived as a scientist yet in the previous episode, The Lunar Excitation (2010). During the gap between seasons 3 and 4, it was decided that Amy should be a neurobiologist, since Bialik has a PhD in neuroscience and could thus portray the character more accurately as the show's neuroscience consultant.

The term "Shamy", that represents a combination of the name Sheldon and Amy, was first introduced by Howard.

Vernee Watson, who plays the triage nurse, also plays the receptionist at the sperm clinic in the pilot. She also played a triage nurse in the season 1 episode The Peanut Reaction (2008), and she played a nurse in Chuck Lorre's other show Two and a Half Men (2003).

S03E23 - The Lunar Excitation (Notes and Trivia)

First appearance of Amy Farrah Fowler (Mayim Bialik). The character is loosely based on Gilda, a character that was cut after the failed first pilot of the show.

The first appearance of Brian Thomas Smith as Zack.

S03E22 - The Staircase Implementation (Notes and Trivia)

In this episode we learn that Sheldon and Leonard's apartment has a flag. It bears a logo identical to that of L?wenbr?u beer.

Sheldon is hilariously wrong when he comments that Raj has wasted his money on his iPod, given that Microsoft would soon make a rival device. The Zune, as it was called, was released in 2006, but discontinued five years later due to disappointing sales that were way behind the iPod.

Sheldon mentions the TV series "Firefly (2002)" and predicts that it will go on for years. This is a joke, as "Firefly" was infamously canceled after just one season.

Sheldon tells Leonard to come back at this very moment in case either of the two of them ever develop time travel. This could be a reference to Stephen Hawking, who once threw a party without invitations to see if a time traveler arrives.

The references to B-Stoff and C-Stoff on Sheldon's white board represent two types of rocket fuel used by the Germans during World War II. They were used in the the V-2 and Me-163 (with T-stoff) respectively.

S03E21 - The Plimpton Stimulation (Notes and Trivia)

Howard reveals he broke up with Bernadette in this episode. It's later revealed in The Hot Troll Deviation (2010), that Bernadette caught him having online sex with a hot troll from World of Warcraft.

S03E20 - The Spaghetti Catalyst (Notes and Trivia)

The purple t-shirt Sheldon wears bears the symbol of DC Comics' Star Sapphire Corp, the members of which wield power rings powered by Love, represented by the purple band of the emotional spectrum.

S03E19 - The Wheaton Recurrence (Notes and Trivia)

Before the scenes set in the bowling alley, when the atoms are shown rotating, one of the orbiting electrons transforms into a bowling ball.

S03E18 - The Pants Alternative (Notes and Trivia)

The song that Sheldon sings at the awards ceremony is "The Elements" by Tom Lehrer and Arthur Sullivan. It is a recitation of the elements (known in 1959 - 102) sung to the tune of "Major General's Song" from The Pirates of Penzance (1983). It is on Lehrer's album 'Songs and More Songs by Tom Lehrer'.

S03E17 - The Precious Fragmentation (Notes and Trivia)

Apart from the scene where Sheldon realizes that he has changed into Gollum from The Lord of the Rings: The Two Towers (2002), there is another parallel from that movie where Sheldon (like Gollum) tries to take the One Ring from the sleeping Penny and Leonard (Frodo and Sam), but they wake up and attack him.

Sheldon's "ketchup" spiel was almost a word for word recitation of a portion of the "ketchup" entry on Wikipedia at the time, with the only difference being that a few other flavorings had been omitted.

The number of prop rings made, as well as what happened to them, as quoted by the characters, actually mirrors the setup of Lord of the Rings as well. Howard claims that 9 prop rings were made (the 9 rings given to the race of Men), 3 were taken home by members of the cast (3 rings were given to the Elves), and the rest destroyed, leaving just this ring (the One Ring). In actuality, many more replicas were made over the course of shooting the films.

S03E16 - The Excelsior Acquisition (Notes and Trivia)

Before Sheldon learns that he will have to go to court instead of getting a comic book signed by Stan Lee, he announces his plan for Lee to sign a Batman comic (despite Lee having had nothing to do with Batman), stating that he will then have "a unique, albeit confusing, artifact." Raj then announces his intention to do the same, de-uniquing Sheldon's intended artifact. Later, while Raj is standing in line, the viewer can see that he plans to follow through with stealing Sheldon's idea as he is holding a Batman comic. Even later, after the signing, while Raj is holding what the viewer is led to believe is the comic that Lee signed for him, it can be seen that the comic is indeed Batman.

Raj repeatedly questions why so many of Stan Lee's characters have alliterative names, including apparently to Stan Lee himself; Stan Lee has stated and written numerous times in real life that the reason is because alliterated names are easier to remember and he didn't want to mix them up.

Sheldon misses out on meeting Stan Lee at a comic book signing because he must appear in traffic court. The nameplate on his bench shows the judge's name is Judge J. Kirby. Jack Kirby was a comic book artist who often worked alongside Stan Lee and helped create some of Marvel Comics' most popular titles.

Sheldon tells Penny, "The moving finger writes, and having writ, moves on". This is a quotation from verse 51 of the Rubaiyat of Omar Khayyam, a collection of poems originally written around the 11th century AD, as translated from Persian into English by Edward FitzGerald (first published in 1859).

The traffic summons that Sheldon receives shows that he was photographed on November 16th driving Penny to the hospital. The episode in which this happens, The Adhesive Duck Deficiency (2009), was indeed first aired on November 16th, 2009.

S03E15 - The Large Hadron Collision (Notes and Trivia)

As Judas was paid with 30 pieces of silver, Sheldon slaps down a tray with 30 pieces of silverware in front of Leonard.

The hotel room number is 714. This is also the street number of the Conner home in Roseanne (1988), a show in which Johnny Galecki (Leonard) co-starred for many years.

The melody Sheldon plays on his recorder is Morgenstemning (Morning Mood) by the Norwegian composer Edvard Grieg, from Peer Gynt Suite No. 1, op. 46.

S03E14 - The Einstein Approximation (Notes and Trivia)

Just before the scene near the end set in the roller disco, when the atoms are shown rotating, one of the orbiting electrons transforms into the glitter ball of the roller disco.

Near the start of the episode, when a frustrated Sheldon throws his whiteboard out the window, you can clearly see the Pasadena City Hall out the window.

When Sheldon serves Howard his bacon cheeseburger, he says it breaks two Jewish dietary restrictions at one time. The first, eating bacon, is widely known, but the second is more obscure: it's the prohibition against eating meat and milk (or any dairy product) together.

S03E13 - The Bozeman Reaction (Notes and Trivia)

Just before Sheldon arrives in Bozeman, the insert with atoms shows one of the orbiting electrons with a map of the United States, in reference to the map that Sheldon has just been using to choose his destination.

Sheldon's map shows two other cities in Montana which are crossed out, which seem to be Helena and Miles City.

The video games that Sheldon had stolen are: Call of Duty (2003), Call of Duty 2 (2005), Call of Duty 3 (2006), Final Fantasy (1987), Final Fantasy II (1988), Final Fantasy IX (2000), Final Fantasy V (1992), Final Fantasy VII (1997), Final Fantasy IV (1991), Final Fantasy VI (1994), Final Fantasy VIII (1999), Halo: Combat Evolved (2001), Halo 2 (2004), Halo 3 (2007), Ms. Pac-Man (1982), Rock Band (2007), Super Mario Bros. (1985), Super Mario Galaxy (2007), The Legend of Zelda (1986), The Legend of Zelda: Twilight Princess (2006) and The Legend of Zelda: Ocarina of Time (1998).

When leaving the apartment, Officer Hackett refers to the other officer as Bochco. Steven Bochco is well known for creating police shows such as NYPD Blue (1993) and Hill Street Blues (1981)

S03E12 - The Psychic Vortex (Notes and Trivia)

Actress Danica McKellar appeared on this episode when Sheldon and Raj meet her character Abby while attending a mixer at the university. In the episode The Bat Jar Conjecture (2008), Raj says, "How about the girl from The Wonder Years (1988)?" He is referring to Danica McKellar, who has a degree in mathematics.

The characters of Abby and Martha are actually a tribute to Joseph Kesselring's Arsenic and Old Lace (1944). Abby and Martha are the names of the homicidal spinster aunts.

The Hindi phrase that Raj says that he said means, "Whatever floats your boat.", the literal translation is: "Whatever keeps you happy."

S03E11 - The Maternal Congruence (Notes and Trivia)

Raj has no lines in this episode. He only appeared in one scene, and as Penny and Beverly were in the room, he did not get a chance to talk. However, he does whisper in Howard's ear to communicate.

Sheldon mentions the professional rivalry between scientists Isaac Newton (1642-1727) and Gottfried Wilhelm Leibniz (1646-1716) over their creation of calculus. Newton and Leibniz concurrently developed "infinitesimal calculus" ("the calculus of infinitesimals") in the late 17th century, while working independently of each other. Newton accused Leibniz of plagiarism, causing a long-term dispute between them.

This is the second Christmas episode in the series; the others are The Bath Item Gift Hypothesis (2008), The Santa Simulation (2012), The Cooper Extraction (2013), The Clean Room Infiltration (2014), and The Holiday Summation (2017).

S03E10 - The Gorilla Experiment (Notes and Trivia)

The technical consultant, David Saltzberg, appears. He was the first person on the left that Howard passed when he entered the dining room introducing Bernadette as his girlfriend to everyone. (Look for the guy in the brown sweater vest at the first table).

This marks the first time Bernadette is in Leonard and Sheldon's apartment. Howard introduces her as his girlfriend.

S03E09 - The Vengeance Formulation (Notes and Trivia)

Fever 104, the radio station Raj mentions, is actually one of the most popular radio stations in India.

Katee Sackhoff's appearance in this episode came about because she accompanied her Battlestar Galactica (2004) co-star Tricia Helfer when she was making a guest appearance on Chuck Lorre's other hit sitcom Two and a Half Men (2003). Lorre approached her about a cameo on The Big Bang Theory (2007). Sackhoff had previously turned down that opportunity in Season 2 when the chance of playing herself went to Summer Glau so she instantly leapt at Lorre's offer.

The chemical reaction that Sheldon uses to get his revenge on Kripke is a genuine one (often used in practical jokes) and is often referred to as "elephant toothpaste". Hydrogen peroxide decomposes slowly to form water and oxygen gas. The presence of potassium iodide catalyzes this reaction, so that it produces large quantities of oxygen very quickly. The gas then causes the liquid detergent to froth copiously as shown. Unfortunaely, the foam created from the reaction can reach temperatures of over 200 degrees and cause severe burns if it comes into contact with a person's skin. Kripke and the others who are dowsed with the foam in the prank could have been seriously injured with burns.

S03E08 - The Adhesive Duck Deficiency (Notes and Trivia)

In this episode, Kunal Nayyar displayed his ear for accents when he accurately imitated costars Johnny Galecki's and Simon Helberg's American accents.

Penny is revealed to have a Chinese character tattoo on her right buttock. Kaley Cuoco, who plays Penny, has an actual Chinese character tattoo on her lower back, as seen in the episode, The Middle Earth Paradigm (2007).

Sheldon's middle name is Lee.

The coordinates Raj gives for the observation site (34.48 N, 118.31 W) refer to the Vasquez Rocks Park, the location of several Star Trek episodes including the one where Captain James T. Kirk rolls a rock onto the reptilian Gorn. A Gorn later make appearances in two of Sheldon's dreams (once in The Apology Insufficiency (2010) in Season 4, and again in The Transporter Malfunction (2012) in Season 5). Also the gang makes one more visit to Vasquez Rocks Park in Season 6's The Bakersfield Expedition (2013) where Leonard gets his car stolen while the gang were taking pictures acting out scenes from Star Trek.

This episode marks the first time Soft Kitty had been sung to anyone other than Sheldon.

This episode mirrors The Vegas Renormalization (2009), with Leonard, Raj and Howard being away while Sheldon and Penny stay at home. The reversal is that this time, Penny is the one who is "kind of sick", and Sheldon having to sing "Soft Kitty" to her (and Penny makes him start over several times).

S03E07 - The Guitarist Amplification (Notes and Trivia)

First mention of Sheldon's father's name: George.

Howard describes the plot of Amazing Spider-man #183 as "Spider-man loses a big fight and then his girl friend splits up with him" This is an accurate description as in that issue Mary-Jane Watson breaks off her engagement to Peter Parker

The actor who appears at the end as Penny's guitarist friend, who is crashed out on the couch in Leonard and Sheldon's apartment, is not credited in the episode.

Though the producers on The Big Bang Theory (2007) don't (typically) allow for improvisations, Stuart's whispering "I love you" to Penny as she walks away in the comic book store is an occasion where an unscripted line was left in the show.

When running away from Penny (Kaley Cuoco) and Leonard (Johnny Galecki) arguing, Sheldon (Jim Parsons) rings Howard (Simon Helberg)'s doorbell. This is one of the few times in the entire series that he calls someone to the door without his ritual of knocking and repeating the name three times.

S03E06 - The Cornhusker Vortex (Notes and Trivia)

At 17:59 in, Kaley Cuoco looks right at the camera for a split second.

Sheldon demonstrates a profound knowledge of football, which came from his father persuading him to watch football games for seven years. Apparently, that ploy stopped working at one point, because in episode 7.9, The Thanksgiving Decoupling (2013), when Sheldon bonds with Howard's father-in-law, he reveals that his knowledge of football comes from his father making him watch before he was allowed to do his homework.

The Battlestar Galactica (2004) Cylon toaster Sheldon is shown using is a real product.

Title Reference: The football team (Nebraska Cornhuskers) Penny and her friends watch and root for and the fact that Leonard gets caught up in trying to understand the sport of football to fit in with Penny's friends.

When Howard and Raj are sitting on a bench after visiting the La Brea Tar Pits, Howard suggests that they go to Marie Callendar's for pie. There actually was a Callendar's restaurant right across the street from (east of) the La Brea Tar Pits, at 5773 Wilshire Blvd. The restaurant closed in 2018, about nine years after this episode aired (and a year before the show ended).

When Raj is watching television in his apartment, the song "Mere Mehboob Mere Sanam" from the film Duplicate (1998) is heard.

When Sheldon asks Penny for bread, he asks, "Have the indigenous fauna accepted you as one of their own? Nudge~nudge~wink~wink." "Nudge~nudge~wink~wink" is a nod to a bit from Monty Python's Flying Circus (1969).

S03E05 - The Creepy Candy Coating Corollary (Notes and Trivia)

Melissa Rauch already uses a speaking voice that is higher-pitched than her own in this episode, but it becomes noticeably higher in subsequent episodes (Rauch's real voice can be heard briefly in The Holographic Excitation (2012) after Howard comments on her squeaky voice). After several appearances, Rauch uses what she said is an imitation of her mother's high-pitched voice.

Sheldon (Jim Parsons) says, "Wesley Crusher had an eidetic memory just like me." The December 10, 1986 casting call featured in Star Trek the Next Generation Companion A Series Guide and Script Library (1999) cites a "photographic memory", while the March 23, 1987 "Star Trek: The Next Generation Writers/Directors Guide" cites "his superior memory".

The Mystic Warlords of Ka'a card game was created by the art department specifically for this episode, which included designing actual playing cards. The designs of several cards (most notably "Enchanted Bunny") have been released by the show's producers since the first airing of this episode.

This episode marks the first appearances on the show for both Melissa Rauch (Bernadette) and Wil Wheaton. It is the first time that Howard meets Bernadette (when Penny reluctantly sets them up on a date), and the first time that Sheldon meets his occasional nemesis, Wil Wheaton (during a game tournament at the comic book store).

Wil Wheaton's t-shirt is from the popular gaming web cartoon Penny Arcade. Wheaton gave the keynote at the Penny Arcade Expo (PAX) 2007.

S03E04 - The Pirate Solution (Notes and Trivia)

When Raj says, "Beefaroni. I think I'll miss you most of all," he is copying the last words that Dorothy says to the Scarecrow just before she leaves Oz for Kansas in The Wizard of Oz (1939).

S03E03 - The Gothowitz Deviation (Notes and Trivia)

Confusingly, the fake tattoo sleeves as described by Howard (Simon Helberg) are actually real genuine products, not just the more commonly known term for arm length real tattoos. Howard and Raj (Kunal Nayyar) are wearing a version described as "realistic nylon mesh tattoo sleeves used in the movie and television industry", similar to women's stockings.

Leonard (Johnny Galecki), Sheldon (Jim Parsons), and Penny (Kaley Cuoco) are watching the anime: Oshikuru: Demon Samurai, which is a reference to episode 2.10 The Salmon Under My Sweater (2004), of Two and a Half Men (2003) in which Charlie (Charlie Sheen) and Jake (Angus T. Jones) collaborate on the theme song to the same show. Both series are created by Chuck Lorre. The actual audio representing Oshikuru: Demon Samurai was from an anime called Boogiepop Never Laughs: Boogiepop Phantom (2000).

Molly Morgan, who plays Bethany, re-appears in episode 8.16, The Intimacy Acceleration (2015), playing the hostess who leads Raj (Kunal Nayyar), Emily (Laura Spencer), Amy (Mayim Bialik) and Leonard (Johnny Galecki) into the Crystal Maze-themed "escape room".

The dance that Penny (Kaley Cuoco) does while making French toast is the exact same dance done by the character Ginger in The Terminator (1984), even to the degree that her hair is up and she is wearing her man's shirt.

When Sheldon (Jim Parsons) says "There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy," he is quoting Hamlet in Act 1 Scene 5 of William Shakespeare's play.

S03E01 - The Electric Can Opener Fluctuation (Notes and Trivia)

Howard previously referred to cyanoacrylates in episode 2.18, The Work Song Nanocluster (2009), as Leonard attempts to define them in this episode.

In the commentary for this episode on the DVD release, the actors actually grew real beards for filming, but they were told to shave them so that the make-up department could put fake ones on. It is never stated why this decision was made.

Just before the first shot of Sheldon with his mother in Texas, there is one of the shots of atoms used to separate scenes. One of the electrons orbiting the nucleus is decorated with the Texan flag.

Leonard preserves a snowflake in a solution of polyvinyl acetal resin (also known as Formvar or Vinylec). This is a real thing. The trick was invented in 1940 by a General Electric researcher in Schenectady, NY, who adapted a technique used to cast copies of aluminum crystallization patterns. Before then, snowflake patterns could only be captured with microphotography.

The title refers to the appliance that Leonard, Howard and Raj used to give Sheldon false results in lieu of killing him.

S02E23 - The Monopolar Expedition (Notes and Trivia)

Howard suggests watching The Thing (1982), presumably because they are in the Arctic. "The Thing" is actually set in the Antarctic; every year, on Midwinter's Eve, the British Antarctic Survey hold a screening of "The Thing".

Marks the first time Sheldon says "bazinga". Parsons credits former show writer Stephen Engel with inventing the word. It became such a catchphrase on the show that a Brazilian species of orchid bee was later named 'Euglossa bazinga' in its honor, especially since this bee had long-time been confused with the Euglossa ignita, and had thus 'fooled' entomologists for years.

Marks the first time when there is a small glimpse of what Mrs. Wolowitz (voiced by Carol Ann Susi) looks like (when Howard (Simon Helberg) holds up his phone to the laptop on which the Koothrappalis skype in from India, there's a thumbnail photo of her on its display.

The title refers to their scientific trip to the far north to find monopoles and prove the validity of string theory.

S02E22 - The Classified Materials Turbulence (Notes and Trivia)

The scene where the guys try to solve Howard's defective waste disposal system with spare parts that are also available to the crew on the International Space Station spoofs a similar scene in Apollo 13 (1995), in which NASA techs on Earth use objects also available to the Apollo 13 crew in an attempt to fix their failing carbon dioxide filtering system. This episode also has a scene where an astronaut calls to Houston to announce "a little situation" (analogous to the famous "Houston, we have a problem" line from Apollo 13).

S02E21 - The Vegas Renormalization (Notes and Trivia)

Raj cites his full name for the first time and we learn his middle name is Ramayan in this episode.

The ringtone on Howard (Simon Helberg)'s phone is Thomas Dolby's "She Blinded Me with Science", the same song used as the theme song in the Unaired Pilot (2006), the original pilot that CBS passed on. Dolby's song was a perfect choice, as his early 80's geeky nerd persona was much like the Big Bang gang.

UK TV channel E4 - which airs The Big Bang Theory (2007) in rotation - has never aired this episode in its daytime slots because of its prostitution storyline.

While checking out Howard's tweets, Leonard calls them "twitters". While this may sound odd now, at that time that's what they were called. Not long after this was originally aired Twitter began to officially call them tweets.

S02E20 - The Hofstadter Isotope (Notes and Trivia)

Howard (Simon Helberg)'s calculations of potential women that they could pick up is based on the Drake Equation, which attempts to calculate odds of finding intelligent alien life in the Milky Way galaxy. Dr. Frank Drake came up with an equation to examine factors of: the rate of star formation (R), the number of stars with planets(fp), the number of planets per solar system suitable for life(ne), the number of those with ACTUAL life(fl), the number of those with INTELLIGENT life(fi), the number of those whose activities emit detectible signs of their life into space where we could find it (fc), and the length of time that those signals are emitted (L).

Sheldon (Jim Parsons)'s assertion that having Bruce Wayne know who murdered his parents destroys any motivation he has for continuing to be Batman comes directly from the works of Chuck Dixon. Dixon is one of the most prolific writers of the Batman comic books, and is the creator of the villainous character Bane (who appeared in Batman & Robin (1997) and The Dark Knight Rises (2012)). His work as a comic book writer has also been referenced in The Punisher (2004) and Batman: The Animated Series (1992).

The comic book over which Sheldon (Jim Parsons) and Howard (Simon Helberg) are arguing is issue #8 of "All Star Batman and Robin" with a variant cover by Neal Adams, issued November 29, 2007.

The comic book Stuart recommends for Penny's nephew is Hellblazer, the basis for Constantine (2005).

This episode marks the first appearance of the comic book store, the first appearance of Kevin Sussman playing Stuart Bloom, and the first appearance of Captain Sweatpants. Kevin Sussman had previously worked in a comic book store in real life.

This is the first episode where the scene transition wipes of atoms also appear at the beginning of the episode. It stays for the rest of the series, only absent in the next episode.

True to Sheldon (Jim Parsons)'s prediction, Dick Grayson did in fact become Batman after Bruce Wayne's death. Specifically this happened in the twenty-one issue "Streets of Gotham" series written by Paul Dini and ran from 2009-2011.

S02E19 - The Dead Hooker Juxtaposition (Notes and Trivia)

The best science joke on the Internet, as Penny calls it, was written and posted online by author Kevin L. Schwartz before it went viral and reached George Smoot. Many of Schwartz's writings are available on Facebook.

The line, "The horror!", was referencing the film Apocalypse Now (1979). Penny speaks this line in a similar fashion in episode 4.17, The Toast Derivation (2011).

The pink, spotted dog seen in the milk crate during Alicia's conversation with Sheldon while she is moving in was previously seen this season on Penny's dining room table.

The title refers to the part that Alicia gets on the CSI television series and Penny's opinion of her.

Valerie Azlynn (Alicia) has, in fact, been in a CSI: NY (2004) episode, but not as a dead hooker.

S02E18 - The Work Song Nanocluster (Notes and Trivia)

A Penny Blossoms website was created as described.

Although it went unnoticed during this episode's initial airing and for several years afterward, Penny's last name is actually revealed here. On the box's address that Sheldon delivers to Penny in the opening scene reads: "Penny Teller." A reference to the magician duo, Penn & Teller. Teller later appeared on the show, playing Amy's father. Contrary to other reports. According to a Looper interview: Prop master Scott L. London said the name "Penny Teller" came from the show's co-creator, Bill Prady, who wanted a pun off of Penn & Teller. Prady added, "I had assurances it wasn't going to be seen, that Scott just needed it for the visual shape of the block of type. But emphatically, Penny's last name is not Teller."

Howard (Simon Helberg) mentions that some type of cyanoacrylate would make a better adhesive. Cyanoacrylate adhesives are more commonly known as Super Glue or Crazy Glue.

Penny (Kaley Cuoco) is seen wearing the Penny Blossom in the next episode The Dead Hooker Juxtaposition (2009). She later wears one to Howard (Simon Helberg) and Bernadette (Melissa Rauch)'s wedding in episode 5.24, The Countdown Reflection (2012).

The fast-paced rhythm-tune to which the boys play Secret Agent Laser Obstacle Chess is from "Sabre Dance" by Aram Khachaturyan.

This was the first episode in this second season not to be directed by Mark Cendrowski.

S02E17 - The Terminator Decoupling (Notes and Trivia)

Earlier, in episode 1.10 The Loobenfeld Decay (2008), Sheldon (Jim Parsons) poses the following riddle to Leonard (Johnny Galecki): "Assuming all the good Terminators were originally evil Terminators created by Skynet, but then reprogrammed by the future John Connor, why would Skynet, an artificial computer intelligence, bother to create a petite hot 17-year-old killer robot?" He is referring to Cameron from Terminator: The Sarah Connor Chronicles (2008) who is played by Summer Glau. In this episode, Glau guest stars as herself.

George Smoot is one of the three Nobel Prize winners to appear in this series. George Smoot had written to the producers of the show and requested to be featured on the series. Smoot, who received Nobel Prize in Physics in 2006, is an admitted fan of the series. The scene involving Smoot was shot at the Warner Brothers Studios in Burbank, California on February 18, 2008. Most broadcasts of this episode in the UK cut Dr. George Smoot's only line, because it refers to crack.

In a future episode during a flashback, the guys mention Firefly (2002) as being a show they would sit down and watch together via the roommate agreement. Summer Glau played River Tam on Firefly.

On their way, Sheldon (Jim Parsons) talks about meeting George Smoot. Leonard (Johnny Galecki) is reading a book, "Wrinkles in Time", which Smoot co-wrote with Keay Davidson.

Penny tells a friend that she only has one shot to play Anne Frank in a one-night play. Kaley Cuoco, who plays Penny, has previously played Anne Frank in the 8 Simple Rules (2002) Season 2 episode Merry Christmas: The Story of Anne Frank and Skeevy (2003).

Terminator: The Sarah Connor Chronicles (2008) went off the air in 2009. Its finale would air on April 10th, 2009, one month after 'The Terminator Decoupling' came out.

The episode was originally intended to feature Katee Sackhoff. Sackhoff would make her first appearance on the show in The Vengeance Formulation (2009) instead.

S02E15 - The Maternal Capacitance (Notes and Trivia)

As Penny and Leonard's mom are going down the stairs at the end of the episode, Penny mentions her father's name being Bob. When her father comes to visit in a later episode, his name is Wyatt.

At the beginning of the episode, the song Sheldon, Raj, and Howard are playing in "Rock Band" is "Under the Bridge" by the Red Hot Chili Peppers.

Christine Baranski received an Emmy nomination for her performance as Leonard's icy mother in this episode.

S02E13 - The Friendship Algorithm (Notes and Trivia)

The "big-balled raccoon" Howard (Simon Helberg) drew on his Sheldon (Jim Parsons) trivia sheet is an example of Bake-Danuki.

The line "Yeah, he's a ginormous knob" spoken by Raj (Kunal Nayyar) in the pre-credit sequence is cut when broadcast by E4 in the UK.

The scene where Sheldon (Jim Parsons) tries to befriend the little girl in the bookshop is used in a training film by London's Metropolitan Police. It is designed to show how people with social disabilities can sometimes be unintentionally inappropriate.

S02E12 - The Killer Robot Instability (Notes and Trivia)

First appearance of Barry Kripke.

In this episode, Leonard says the name of his childhood bully was Jimmy Mullins. Jimmy Mullins was mentioned in Season 4 of Roseanne (1988), the same season Johnny Galecki joined the cast of the show.

The "Southern California Robot Fighting League" is a fictitious robot fighting championship. However, BattleBots is a real televised competition that aired from 2000-2002 and was reprised in 2015. This 'The Big Bang Theory' episode aired on Jan. 12, 2009 during the hiatus between the two series runs.

S02E11 - The Bath Item Gift Hypothesis (Notes and Trivia)

At the end of the episode, Leonard (Johnny Galecki) comments "It's a Saturnalia miracle!" in response to Sheldon (Jim Parsons) hugging Penny (Kaley Cuoco). Saturnalia is an old Roman festival where, among other things, gifts were given, but also an overturning of Roman social norms were performed. The "overturning" of Sheldon's "social norm" of minimal physical contact with people is probably Leonard's meaning.

Michael Trucco is a part of the Battlestar Galactica (2004) cast which is one of Sheldon's favorite shows.

The fictional store at which Sheldon buys Penny's gift is called Le Bain Quotidien {'The Daily Bath'), a pun on the phrase 'le pain quotidien' (daily bread).

The MacArthur Genius Grant is real. It is an annual prize awarded by the John D. and Catherine T. MacArthur Foundation to U.S. citizens typically to between 20 and 40 working in any field, who "show exceptional merit and promise for continued and enhanced creative work". There is no application process. The award is voted on by an anonymous committee and the recipient is notified via a phone call.

The napkin really is signed by Leonard Nimoy. A photograph exists of Jim Parsons holding it up.

S02E10 - The Vartabedian Conundrum (Notes and Trivia)

Sheldon does in fact sing an octave above Middle C. Either Jim Parsons has perfect pitch, or he had some kind of audio cue to match the pitch.

S02E09 - The White Asparagus Triangulation (Notes and Trivia)

Sheldon (Jim Parsons) attempts to invoke "Starfleet General Order 104 Section A" to relieve Leonard (Johnny Galecki) of his command of his own relationship with Stephanie (Sara Rue). This section has not been clearly spelled out in a Star Trek episode, though the two sections that follow it (B and C) have.

Sheldon is correct in that a strawberry is not a fruit (it is derived from the ovary of a plant). It is actually an accessory fruit (derived from some tissue around the plant's ovary).

S02E08 - The Lizard Spock Expansion (Notes and Trivia)

The game of "Rock Paper Scissors Lizard Spock" was invented by a software engineer named Sam Kass, who outlined the rules and hand gestures on his website in 1998. He, however, called it "Rock Paper Scissors Spock Lizard".

S02E07 - The Panty Pinata Polarization (Notes and Trivia)

The two models who open the door for Raj (Kunal Nayyar) and Howard (Simon Helberg) are Lio Tipton and Samantha Potter, who were actual contestants on America's Next Top Model (2003). In their cycle, they placed third and second, respectively.

When Howard (Simon Helberg) sarcastically chants "One of us, one of us" after Leonard says "You're officially one of us!", this is an homage to the 1932 film Freaks (1932) where deformed humans are joyfully chanting for the female protagonist Cleopatra (to whom Penny is being compared) "Gooble gobble! We accept her! One of us! One of us!"

When Leonard (Johnny Galecki) gives Penny (Kaley Cuoco) the number for Sheldon (Jim Parsons)'s mother, he paraphrases Harry S. Truman's secretary of war, Henry L. Stimson, who justified the use of the Atomic Bomb by stating that it will shorten the war by five years and save millions of lives.

S02E06 - The Cooper Nowitzki Theorem (Notes and Trivia)

According to Sheldon's schedule, Mondays he eats Thai food consisting of Mee krob and chicken satay with extra peanut sauce from Siam Palace; Tuesdays are new comic book night at the Comic Book store; Wednesdays he plays "Halo" and/or watches Battlestar Galactica (2004); Thursdays he has pizza from Giacomo's. Sausage, mushrooms, light olives; Friday is "Vintage game night" (mentioned earlier in The Codpiece Topology (2008)). On weekends he plays paintball.

During the montage, the song "You Can Be My Yoko Ono" by Barenaked Ladies, who also sing the show's theme song, is played. Romona is being compared to Yoko Ono who was John Lennon's wife and is often blamed for the break-up of The Beatles.

First mention of the friendship/roommate agreement between Sheldon (Jim Parsons) and Leonard (Johnny Galecki).

Riki Lindhome (Ramona) originally auditioned for the role of Penny.

Riki Lindhome (Ramona), is half of the comedy singing duo known as Garfunkel & Oates, along with Kate Micucci. Both girls have appeared, separately, as characters on "The Big Bang Theory". Lindhome appeared in three episodes as Sheldon's grad school assistant and admirer, Ramona Nowitzki. Her crush on Sheldon eventually leads to him proposing to Amy Farrah-Fowler. Micucci appeared in eight episodes as Raj's painfully shy girlfriend, Lucy.

Sheldon doesn't eat at unknown restaurants, for fear that they would try to pass off a "trident" (three tines) as a fork (four tines). He mentions that "tridents are for ruling the Seven Seas", because in ancient mythology, Poseidon/Neptune, the Greek/Roman God of the Sea, controlled the waters and grounds with his trident.

The comic book which Ramona catches Sheldon reading inside his textbook is Batman #680, cover-dated October 2008.

The title refers to the suggestion by Sheldon's groupie Ramona Nowitzki for the theorem that she had been helping him with so that they would be sharing credit. This is also the first episode in which the title is mentioned within the dialogue, a rarity for the show.

S02E05 - The Euclid Alternative (Notes and Trivia)

Gives a rare camera view of Leonard and Sheldon's apartment, from the vantage of the hallway that's normally seen to the back right, going to the bedrooms, allowing us to see the "4th wall" in the front of the apartment the camera normally sees through.

Sheldon complains about the check engine light in Penny's car for the first time. It becomes a running joke in the rest of the series. The first time is in episode 2.5 The Euclid Alternative (2008), later mentioning it again in episodes 2.14 The Financial Permeability (2009), 3.8 The Adhesive Duck Deficiency (2009), and 3.21 The Plimpton Stimulation (2010). Leonard's mother (Christine Baranski) similarly makes a point of this observation in episode 3.11 The Maternal Congruence (2009), as does Amy Farrah Fowler (Mayim Bialik) in episode 4.1 The Robotic Manipulation (2010). Penny says, "The light has been on since I bought the car," in episode 3.8 The Adhesive Duck Deficiency (2009). The car eventually dies and Leonard buys her a new one.

Sheldon is correct in his assertion that Second Street is the most common street name in America. This is according to The National League of Cities which lists 10,866 streets with that name. First Street is actually third on the list behind Third Street.

The first proper appearance of Sheldon's signature triple knock: "Knock-knock-knock, Penny? Knock-knock-knock, Penny? Knock-knock-knock, Penny?" He used a similar knock in The Loobenfeld Decay (2008), but it consisted of four knocks followed by a name, rather than three knocks.

The last scene is a parody of The Phantom of the Opera (1925).

While Leonard (Johnny Galecki) is watching Sheldon (Jim Parsons) drive the simulator if you listen closely you can hear Leonard say Jim, which is Sheldon's real name.

Years after appearing together in this episode, Jim Parsons and Octavia Spencer starred alongside each other in Hidden Figures (2016), which was nominated for three Academy Awards, including Best Picture.

S02E04 - The Griffin Equivalency (Notes and Trivia)

At The Cheesecake Factory, Raj is drinking his trademark Grasshopper.

Charlie Sheen was a guest star in this episode and at the time was starring in Chuck Lorre's other production Two and a Half Men (2003) as Charlie Harper. Sheen's appearance led to widespread speculation that Two and a Half Men and The Big Bang Theory were set in the same continuity, but later episodes of Two and a Half Men proved otherwise.

Final appearance of Dr. Gablehouser, played by Mark Harelik.

Raj's planetary object, 2008-NQ17, is fictitious, though its designation implies that it was the 220th minor planet discovered during the first fifteen days of July 2008; although analysis of old photographs can result in late additions, considerably fewer than 220 discoveries have been made over that period and it is highly unlikely that number will ever be assigned.

The red t-shirt that Sheldon is wearing (while he's eating Chinese food with Leonard & Howard) bears the distinctive logo of The Greatest American Hero (1981), a comedy/adventure TV series from the early 1980s, about a young man who is given an alien suit that grants him superpowers.

This is the first time Sheldon (Jim Parsons) says his famous line "I'm not insane. My mother had me tested."

Title reference: Sheldon wanted to replace his childhood cat with a griffin, as he thought it would better suit his needs for a companion. He uses the story as a springboard to discuss a replacement for Raj.

When Leonard comments on Sheldon's forced smile, he says that they are there to "cheer up Koothrappali, not kill Batman". He refers to Batman's mortal enemy, The Joker, who always grimaces menacingly.

When Raj's apartment is shown, the viewing audience sees that he has at least two telescopes: a small refractor and a larger (perhaps 8") Schmidt-Cassegrain reflecting telescope on a computer-controlled mount. On a shelf, he also has an "L"-shaped military-style flashlight fitted with a red filter. Astronomers use red flashlights like this one in the field to avoid ruining their night vision. A refractor is a telescope in which the light passes through a series of lenses instead of being reflected in mirrors.

S02E03 - The Barbarian Sublimation (Notes and Trivia)

This episode was watched by 9.33 million people with a rating of 3.7 (adults 18-49).

S02E02 - The Codpiece Topology (Notes and Trivia)

This episode was watched by 8.76 million people with a rating of 3.3 (adults 18-49).

S02E01 - The Bad Fish Paradigm (Notes and Trivia)

A Munchhausen Trilemma is a reasoning that no Truth can be proved, since any proof will ultimately fall into one of three unsatisfactory reasonings. In Sheldon's case: he's moving out, because he's moving out.

Pasadena City College does exist and offers Paralegal Studies).

Sheldon (Jim Parsons)'s list of Catwoman actresses, from most favorite to least: Julie Newmar, Michelle Pfeiffer, Eartha Kitt, Lee Meriwether, Halle Berry.

Sheldon's slip about being denied clearance to a secret research facility may be true, as there was a secret government-funded military super-collider hidden beneath a fake agricultural station 12.5 miles southeast of Traverse City, Michigan in the Traverse City Forest Area until 1993.

S01E17 - The Tangerine Factor (Notes and Trivia)

At the end of this episode, note the sport coat and pink dress worn by Leonard and Penny. The same clothes are worn in the season 2 premiere, implying that the season premier was the continuation of their first date.

By coincidence, both this episode and an episode of the Fox drama Bones (2005) (The Pain in the Heart (2008)), which aired on the same night, May 19, 2008, reference Schr?dinger's cat.

Sheldon is correct in stating that light-years are a measure of distance, not time. One light-year is the distance that light traverses within the span of one year, which is about 5.88 trillion miles (a trillion being one million millions) or 9.46 trillion kilometers.

The first of many times in the entire series where Penny mentions she has a sister. Later on, only her brother Randall (Jack McBrayer) is introduced, at the second wedding of Penny and Leonard. Even though the sister is eventually named Lisa in The Donation Oscillation (2019), she never made an appearance on the show.

The 'little crush' that Menelaus had on Helen of Troy was enough to launch the Trojan War when Paris of Troy stole her away.

The Schroedinger's cat analogy recurrent through the show is mentioned again in The Codpiece Topology (2008), wherein Penny mentions it to a guy she goes out with, as well as in The Russian Rocket Reaction (2011), wherein Sheldon refers to "Schroedinger's Friendship".

Through the Looking Glass was Lewis Carroll's sequel to "Alice In Wonderland". Like Alice, it too has a strong chess-centered theme. Alice goes through the looking glass, i.e. mirror, to another world where things are recognizable, yet turned sideways. The phrase "through the looking glass" is a metaphor for any time the world turns strange, insane, or otherwise abnormal, as if one were on the other side of the mirror.

S01E16 - The Peanut Reaction (Notes and Trivia)

Howard tries to bribe the nurse with "the man who freed your people", i.e. Abraham Lincoln, meaning a $5 bill. She responds with a demand for "Benjamin Franklin and his five twins". Franklin is on a $100 bill, so she wants $600.

Howard tries to lure Leonard out of his apartment by inviting him to a new "definitive cut of Blade Runner (1982) with 8 seconds of previously unseen footage", that supposedly "completely changes the tone of the film". This is a stab at the fact that there are at least five different versions of Blade Runner (1982) (including a Director's Cut that the director wasn't fully satisfied with, leading to a Final Cut). One of the most notable additions to later versions was a brief dream sequence of about 20 seconds that has since become the subject of intense fan debate about the exact meaning of the film.

Sheldon's statement about horoscopes being hokum is based on the work of Bertram Forer, a psychologist from UCLA. His classic 1948 experiment involved administering personality tests to groups of subjects, and then giving each subject the same exact personality evaluation (copied from a newspaper astrology column) and asking them to evaluate the accuracy of the results on a scale of 1 to 5. The average accuracy was rated at an incredible 4.2, indicating that people are generally willing to accept generalized descriptions of themselves because they WANT them to be true. This experiment has been repeated hundreds of times by various researchers; always with almost exact results, giving us "The Forer Effect" or "subjective validation".

The ER nurse, Althea (Vernee Watson), is the same person (or at least the same actress) as the waiting room nurse in the sperm bank from the Pilot (2007).

The man in the D-Link Wireless Network Adapter box is director Mark Cendrowski.

This is the third time that Penny (Kaley Cuoco) kisses Leonard (Johnny Galecki). She first kissed him after her Halloween party in The Middle Earth Paradigm (2007) and in The Nerdvana Annihilation (2008), although only in a dream but she did kiss him on the cheek just before her date Mike came up the stairs.

S01E15 - The Pork Chop Indeterminacy (Notes and Trivia)

Howard's belt buckle is The Flash.

In the beginning of the episode, Howard mentions a project he is working on that will take him up on the next space shuttle. This eventually happens in Season 5.

Leonard, Howard and Rajesh all sit in Sheldon's spot at some point.

Missy (Courtney Henggeler) calls Sheldon (Jim Parsons) by his nickname, "Shelly", just like their mother (Laurie Metcalf).

Missy tells Leonard and Howard that when they were eight years old, Sheldon tried to build an armed robot to keep her out of his room. However in Young Sheldon (2017) it is shown that Missy and Sheldon actually share a room. (Though it is possible that when Sheldon refers to "his room", he is in fact referring to his side of the room. A common distinction when siblings share a room.)

Prior to her appearance at Sheldon and Amy's wedding in episode 11.24, the only other appearance of Missy occurs when you can hear her screaming during childbirth in The Cooper Extraction (2013).

Sheldon tells his sister that he weighs 165 pounds.

The original title, still used internationally in English-speaking territories, is "The Shiksa Indeterminacy".

There are four framed comic books on Sheldon's bedroom wall: Lois Lane, Superman, The Flash and Secret Origins.

This is the third time that Raj (Kunal Nayyar) is able to talk to a girl. Previously, it took alcohol, another time was accidental and this time it's an experimental drug trial.

S01E14 - The Nerdvana Annihilation (Notes and Trivia)

During Sheldon's dream, the time machine's display reads "802,701". This is the same year in which Rod Taylor stops in the 1960 movie The Time Machine (1960).

Johnny Galecki and Kaley Cuoco have since admitted that the scene when Leonard has the dream where he saves Penny by taking her down the elevator shaft was the start of their relationship. They had crushed on each other before, but afterwards realized they needed to go for it.

Raj (Kunal Nayyar) said he will match the offer for Leonard (Johnny Galecki)'s collectibles plus a 1000 Rupees and Sheldon (Jim Parsons) asked "What's the exchange rate?". Raj replied "None of your business". 1000 Indian Rupees is approximately 22 USD.

Sheldon mentions that Captain Kirk stole a cloaking device from the Romulans on Stardate 5027.3. He's referring to the the events of The Enterprise Incident (1968).

The date on the time machine during Sheldon's (first) dream is April 28, the same date that this episode first aired.

The Time Machine in this episode is a replica not the original from The Time Machine (1960). The original is owned by film collector Bob Burns who declined the use of it for the show.

S01E13 - The Bat Jar Conjecture (Notes and Trivia)

Howard's checkerboard belt buckle in the opening scene is the same design as the 'Jaunting belt' used in Series 3 and 4 of the 1970's UK TV series The Tomorrow People (1973).

Queen's "We Are the Champions" plays during Howard(Simon Helberg)'s triumphant moment at the 29th Annual Physics Bowl. Fittingly, the lead guitarist for that song, Brian May, is an astrophysicist.

Raj suggests "the actress who played TV's Blossom" for their physics bowl team to replace Sheldon. That actress, Mayim Bialik, does have a Ph.D. in neuroscience. Bialik joined the show in the Season 3 finale and became a regular cast member in Season 4 as Dr. Amy Farrah Fowler. Raj also says, "How about the girl from 'The Wonder Years'?" He is referring to Danica McKellar, who has a degree in mathematics, coauthored a physics theorem, and appears in the Season 3 episode The Psychic Vortex (2010) as Abby. Coincidentally, in The Wonder Years (1988), her character's last name is Cooper.

The Batman cookie jar is a regular prop for the remainder of the show's run.

The final question in the Physics Bowl round is a Feynman diagram. Named for their inventor, Richard Feynman, these diagrams visually represent the behavior of subatomic particles.

S01E12 - The Jerusalem Duality (Notes and Trivia)

Leonard (Johnny Galecki) says "A bad feeling I have about this!" doing a Yoda impression. The line "I have a bad feeling about this" is said in every episode of the main Star Wars series, although Yoda (also from Star Wars) would probably have said "A bad feeling about this I have!".

Sheldon (Jim Parsons)'s comment about Dennis (Austin Lee) seeing The Matrix (1999) supposes that Dennis Kim is able to detect the "real" reality, from which the movie series takes its name, in which mankind is actually enslaved by machines who live off of human body heat and electrochemical energy. Most people, as depicted in the series of movies, are in a sort of state of hypnosis, living an artificial reality imposed on them.

The "shelf" Howard (Simon Helberg) is building is actually an inverted Kodiak Sidewinder motorized step (painted silver), used for entering/exiting lifted trucks.

When Dennis Kim (Austin Lee) enters Sheldon (Jim Parsons)'s office, his whiteboard features a massless two-loop self-energy diagram and the evaluation of the associated multiloop Feynman integral. Multiloop Feynman integrals appear when quantum-field amplitudes are constructed within perturbation theory. They are integrals over so-called loop momenta. Feynman integrals are usually complicated objects even in a one-loop approximation, so that the number of loops equal to two is already considered big.

S01E11 - The Pancake Batter Anomaly (Notes and Trivia)

Leonard (Johnny Galecki), Howard (Simon Helberg) and Raj (Kunal Nayyar) attend a Planet of the Apes marathon in an effort to avoid Sheldon (Jim Parsons) when he is sick. Before the Marathon begins Leonard cracks his glasses which is reminiscent of the classic The Twilight Zone (1959) episode, Time Enough at Last (1959), which was penned by Rod Serling. Serling also wrote the screenplay for the original Planet of the Apes (1974).

Sheldon refers to Penny as "Typhoid Penny" when inquiring as to which pathogen she has introduced as an analogy to "Typhoid Mary". Mary Mallon was a carrier of typhoid fever and many people she came into contact with died of it, although she showed no symptoms.

Sheldon tells Penny that he has an IQ of 187.

The domed building visible from Leonard and Sheldon's apartment window is the Pasadena City Hall.

The pseudoscalar meson nonet is clearly seen on the small refrigerator blackboard, which is what Eric Gablehauser was "doodling" in The Luminous Fish Effect (2007).

The three-dimensional chess game was often seen in Star Trek: The Next Generation (1987), one of Leonard and Sheldon's favorite shows. Cast members Wil Wheaton, LeVar Burton and Brent Spiner would make cameos later in the series, with Wheaton having a recurring role. It was also used in the original Star Trek (1966) series as well.

The waitress who warns Penny about the "homeless crazy guy at table 18" is the same woman who Raj met and went home with at Penny's Halloween party in The Middle Earth Paradigm (2007).

This is the first time Sheldon makes Penny sing "Soft Kitty" for him (a lullaby that Sheldon's mother used to sing him when he was sick). The tune is sung again in several subsequent episodes, including one (The Adhesive Duck Deficiency (2009)) where Penny turns the tables on Sheldon and makes him sing "Soft Kitty" to her.

S01E10 - The Loobenfeld Decay (Notes and Trivia)

This episode starts Sheldon's habit of repeatedly knocking on a door while repeatedly calling out to the person, although it is a series of four knocks instead of three.

S01E09 - The Cooper-Hofstadter Polarization (Notes and Trivia)

As Penny (Kaley Cuoco) and Sheldon (Jim Parsons) are walking up the stairs, and they discuss Sheldon's disagreement with Leonard (Johnny Galecki), Penny asks Sheldon "How do you feel?". Sheldon looks a bit confused and states "I do not understand the question". This is in homage to Star Trek IV: The Voyage Home (1986), the computer used to retrain Spock's mind asks him the exact same question ("How do you feel"), which Spock likewise responds "I do not understand the question".

Sheldon says that Occam's Razor suggests that someone threw the letter in the trash can. Occam's Razor is the principle developed by the philosopher William of Occam in the fourteenth century that states that of many competing explanations for a phenomenon, the simplest one is likely to be the correct one.

The 30 second video shot by Howard "Physicists Gone Wild!" is a real video which was available on YouTube.

The swelling music Leonard, Sheldon, Howard and Raj are pantomiming to when Penny walks in, commonly referred to as the "Theme from '2001: A Space Odyssey,'" is the introduction to the 1896 tone poem "Thus Spoke Zarathustra," by Richard Strauss (1864 - 1949), inspired by the novel of the same name by Friedrich Nietzsche (1844 - 1900). The introduction is also known as "Hymn to the Sun," from the beginning of "Zarathustra's Prologue". However, the guys' pantomiming indicates they're referencing 2001.

This was the first episode written after the 2007-2008 Writers Guild of America strike. During the hiatus enforced by the strike, CBS officially renewed the series for a second season.

S01E08 - The Grasshopper Experiment (Notes and Trivia)

Sheldon's request for a Virgin Cuba Libre made with Diet Coke is reminiscent of the famous scene in Five Easy Pieces (1970) in which Bobby Dupea (Jack Nicholson) wants a side order of wheat toast, but the waitress tells him they don't serve side orders of wheat toast. Bobby then orders a chicken salad sandwich on wheat toast, but asks the waitress to hold the mayonnaise, butter, lettuce, and the chicken. He then tells her, "...bring me the toast, give me a check for the chicken salad sandwich, and you haven't broken any rules."

This episode was originally titled The Slippery-Nipple Effect.

This episode was the final one to air before the 2007-2008 Writers Guild of America strike, which put a hiatus on television production for three to four months.

This is the first episode where Raj Koothrappali is able to speak to a woman after imbibing alcohol. Up until this time (for the first seven episodes), Raj didn't drink. But he is so upset about being pressured by his parents to get married, that he decides to take up drinking (when Penny wants to practice making drinks for her new bartender job). Penny makes Raj a grasshopper cocktail, and after taking a sip, he begins talking to Penny without even realizing what is happening. When Penny points out that he is talking to her, Raj adopts the habit of drinking alcohol whenever he needs to speak with a woman.

S01E07 - The Dumpling Paradox (Notes and Trivia)

As Chen (the waiter at the Chinese restaurant) leaves Sheldon (Jim Parsons), Leonard (Johnny Galecki) and Raj (Kunal Nayyar)'s table, he mutters "Young idiot" under his breath in Cantonese.

At Szechuan Palace, Sheldon explains that the gang's standard order includes the steamed dumpling appetizer, consisting of four dumplings to be divided among the four of them. Later, in The Dead Hooker Juxtaposition (2009), Sheldon is horrified when his dumplings are steamed, exclaiming that "...you hear stories of this sort of thing, but you never think it'll happen to you".

The waiter in the Chinese restaurant (Chen) is played by James Hong, the same actor who played the host of the restaurant in the classic Seinfeld episode, The Chinese Restaurant (1991). Hong also played a brief part in Blade Runner (1982), the movie that Howard wants to take Leonard to later in the season in The Peanut Reaction (2008).

This episode is the first time Penny hears Raj speak. Raj is unable to speak while Penny is in the room because of his anxiety disorder, so the most she has heard before now is a strangled half syllable. At the end of this episode Raj speaks while playing Halo. He's not aware of Penny's presence so the anxiety disorder isn't an issue. The characters don't comment on this milestone.

S01E06 - The Middle-earth Paradigm (Notes and Trivia)

It is revealed that Leonard (Johnny Galecki)'s middle name is Leakey. Leonard's father once worked with anthropologist Louis Leakey.

Rachel Cannon and Brian Patrick Wade were also on Two and a Half Men (2003), just like Jodi Lyn O'Keefe(The Vegas Renormalization (2009)), Valerie Azlynn(The Dead Hooker Juxtaposition (2009)), and Brooke D'Orsay (The Dumpling Paradox (2007)). Even Charlie Sheen had a guest spot in The Griffin Equivalency (2008)). Both shows were created by Chuck Lorre.

S01E05 - The Hamburger Postulate (Notes and Trivia)

Howard talks of Leonard and Leslie making eine kleine bang bang music. "Eine Kleine Nachtmusik" is Mozart's most popular piece for string quartet, although today it is often performed by a string orchestra.

It is revealed here that Sheldon (Jim Parsons) went to college at the age of 11.

Johnny Galecki (Leonard) knows how to play the cello in real life.

Johnny Galecki and Sara Gilbert were former costars on Roseanne (1988).

Leonard (Johnny Galecki) states, "Orcs are magic, Superman is vulnerable to magic...", Superman's powers are derived from the yellow sun of Earth; they have no magical component, leaving him open to malignant sorcery. On the other hand, Superman similarly battles an ogre in Justice League of America Vol. 1 #49 (November 1966) with no ill effect.

When just Leonard and Leslie go back over the section together, Leonard draws the bow over the cello the correct way when he plays a note to tune it. But when he actually starts playing the part with Leslie, he has flipped the bow around so that the wooden side is touching the strings. Since Johnny Galecki knows how to play the cello, he might have done this intentionally to avoid playing any real sound causing a conflict when they added the music in post. When he does his tuning note, he can then be seen twisting it upside down for the fake playing.

S01E04 - The Luminous Fish Effect (Notes and Trivia)

Mary Cooper, Sheldon's mom, reveals Sheldon was born in a K-mart.

On Dr. Gablehauser's shelf are two photographs. One is of him shaking hands with Bill Clinton. The other shows him talking to President George Bush.

Sheldon weaving on the loom is mentioned again in The Toast Derivation (2011), where it is revealed that he made matching serapes for Leonard, Howard and Raj, the latter most of which who still wears it when the weather gets cold.

This is the first look into Sheldon's bedroom. The main items seen include: Red lightning print, framed, to the left of the closet; Green and black photo or image, framed, to the left of the bedroom door; Seville laundry sorter behind the bedroom door; Building the Golden Gate Bridge poster behind the bedroom door; Golden Gate Bridge 3-D metal rendering on the dresser; Wicker basket on the dresser; Media drawers on the dresser; Triple Deception (1956) posters over the dresser/bookshelf; Sterilite black storage crates on the bookshelf; Apogee desk lamp on the nightstand; Blue Brentwood bedrest/reading pillow on the bed; Comic: Green Lantern #8 (1961) over the bed; Comic: Strange Adventures #140 (1962) over the bed; Comic: Superman #197 (1967) over the bed; Comic: DC Special #17 featuring Green Lantern (May 1975 issue) over the bed; Comic: Batman #592 (December 1993), in the bins on the shelf; Comic: Superman: Man of Steel #29 (January 1992 issue), in the bins on the shelf; Above the bed: blueprint of the Golden Gate bridge.

Title Reference: Sheldon produces glow-in-the-dark fish in this episode.

S01E03 - The Fuzzy Boots Corollary (Notes and Trivia)

Howard refers to Isaac Asimov's Three Laws of Robotics which were introduced in his 1942 short story "Runaround".

Johnny Galecki and Sara Gilbert previously played boyfriend/girlfriend, and then husband/wife, on Roseanne (1988).

Leonard (Johnny Galecki)'s full name is Leonard Leakey Hofstadter.

Sheldon seems very against getting a cat and Leonard implies he is allergic to cats. However, in The Zazzy Substitution (2010), after his break up with Amy Farrah Fowler, Sheldon adopts 20 cats and says he has a great affinity for cats.

The song that Leonard (Johnny Galecki) is singing is "Boston" by Augustana.

Title reference: "Fuzzy Boots" was one of the names that Leonard was considering for his cat.

S01E02 - The Big Bran Hypothesis (Notes and Trivia)

Both apartments appear to have doorbells no one uses and aren't there later.

In a nod to the classic short, the Music Box, which starred Laurel & Hardy, and to the legendary Sisyphus, Sheldon and Leonard struggle in this episode to get an entertainment center in a large crate up the stairs to Penny's apartment.

Leonard mentions his collection as having 2,600+ comic books.

Penny has a copy of the 2006 best-selling self-help book "The Secret." The basic premise of this book is the magical notion that whatever you choose to visualize will become reality. Belief in such new-age subjectivism is the opposite of the objective scientific approach which Leonard and Sheldon espouse.

Penny's apartment layout changes throughout the show; here it is shown that she has a balcony, while later in the show the balcony is gone and the bedroom is where the balcony used to be.

Sheldon mentions the Mandelbrot Set of complex numbers. He's referring to a set of points in the complex plane that is self-replicating according to a predetermined rule such that the boundary of the set has fractal dimensions, which is most often used in the study of fractal geometry. This is part of chaos theory. Sheldon mentions this in reference to the chaos in Penny's messy apartment.

The guys mention that they are having a Superman movie marathon. Later in the episode, upon seeing how messy Penny's apartment is, Sheldon exclaims "Great Caesar's Ghost!" which was Perry White's catchphrase on Adventures of Superman (1952).

The title refers to the cereals that Sheldon stores on top of the refrigerator, sorted by fiber content, specifically the highest fiber cereal, "Big Bran."

This is the only time where a different camera angle for the staircase is seen, when they are trying to push up Penny's furniture.

S01E01 - Pilot (Notes and Trivia)

Darth Vader Shampoo and Luke Skywalker Shampoo actually exist, but there isn't a conditioner.

Howard's belt buckle is a Nintendo controller.

Leonard (Johnny Galecki) and Sheldon (Jim Parsons) buy lunch from House of Tandoori, which is a real restaurant in Pasadena.

Leonard (Johnny Galecki) states that the combined IQ of Sheldon (Jim Parsons) and himself is 360. In a later episode of season 1 Sheldon states his IQ as 187 meaning that Leonard's IQ is 173.

Penny offers to pay for dinner near the end of the episode. This is one of the few times Penny is assumed to be responsible for paying for food during the show's entire run. It is a long-running plot point that Penny does not pay for food. This is the only time she actually offers to pay for her food and the food of others when she says, "Dinner is on me."

Raj (Kunal Nayyar)'s hat in this episode has the number 42 on it, likely paying homage to Douglas Adams's book Hitchhikers Guide To The Galaxy where the answer to the ultimate question of life, the universe and everything is 42.

The opening scene at the sperm bank was cut for syndication. Showrunner Chuck Lorre realized that the scene was no longer compatible with the rest of the show, where Sheldon is so protective of his DNA that he would never sell it so carelessly at a sperm bank. It is also established later on that Sheldon has plenty of savings, removing the need for him to earn quick money that way.

The receptionist in the sperm bank was played by Vernee Watson. Watson has played a nurse in nearly every episode that a character has ended up in the hospital. Including Bernadette's first birth and the time Sheldon needed a haircut. More recently she continued that streak when she time traveled and appeared in Young Sheldon (2017) as Nurse Robinson.

The scene where Sheldon (Jim Parsons) and Leonard (Johnny Galecki) observe Penny (Kaley Cuoco) through her open apartment door would be repeated as an homage in the series' 100th episode (The Recombination Hypothesis (2012)). The characters would even be dressed similarly, right down to Penny wearing the exact same blue top that she wears here.

The sign on the wall at the sperm bank reads "Donations Assistance Materials Available."

The song that Howard (Simon Helberg) sings in the car at the end is "Baby, Don't Get Hooked on Me" originally recorded by Mac Davis.

This is the only episode where Raj (Kunal Nayyar) is seen with a hat.

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