Big Bang Theory Quote
Leonard: Okay, so, it wasn't until his 21st birthday that Biff had will have placed his first bet and made his millions. That's when he altered the timeline.
Sheldon: Yeah, but he had will haven't placed it!
Howard: What?
Sheldon: Unlike Hot Tub Time Machine, this couldn't be more simple. When Biff gets the almanac in 1955, the alternate future he creates isn't the one in which Marty and Doc Brown ever use the time machine to travel to 2015. Therefore, in the new timeline, Marty and Doc never brought the time machine...
Leonard: Wait. Is "brought" right?
Sheldon: (thinking) Marty and Doc never... had have had brought?
Leonard: ...I don't know. You did it to me.
Sheldon: Oh, I'm going with it. Marty and Doc never had have had brought the time machine to 2015. That means 2015 Biff could also not had have had brought the almanac to 1955 Biff. Therefore, the timeline in which 1955 Biff gets the almanac is also the timeline in which 1955 Biff never gets the almanac. And not just never gets. Never have, never hasn't, never had have hasn't.
Quote from S08E05 - The Focus Attenuation