The Big Bang Theory Episode 7.11 The Cooper Extraction

Sheldon has to go back to Texas when he learns that his sister is going into labor, leaving the rest of the gang to prepare for Christmas without him. As they gather to begin decorating the apartment tree, they begin to wonder what their lives would have been like if none of them had ever met Sheldon, imagining various scenarios from that alternate reality. Wolowitz postulates that he'd still be living with his mother, though he'd have killed her long ago, ala Psycho. Bernadette argues that she probably never would have married Wolowitz, given that he and Koothrappali can act like a gay couple from time to time. Amy states that Penny wouldn't have been able to resist Sheldon's raw sexuality and would've tried to sleep with him long ago. Throughout the various fantasy sequences, Sheldon calls them via Facetime to complain about the messy, disgusting delivery process, but Amy convinces him to stay the course and be there for his sister. The gang then comments on how much of a positive impact Amy has had on Sheldon, and Leonard proves it to her by showing her that Sheldon made a picture of her his desktop screensaver.