Big Bang Theory Quote
Sheldon: (after informing Stephanie he had successfully made his own CAT scanner at the age of 12) In fact I was briefly able to see the inside of my sister's guinea pig, Snowball, before he caught fire. It led to an interesting expression in our house: "Not a Snowball's chance in a CAT scanner!"
Quote from S02E09 - The White Asparagus Triangulation