CBS

Season 4: Episode 17 - The Toast Derivation

The Toast Derivation: ­With Leonard dating Priya and Priya staying with her brother, Raj, the gang starts hanging out at Raj's place, much to Sheldon's disbelief. Amy Farrah Fowler helps with him the startling realization that it is Leonard who is the social center of their group and not Sheldon. Undeterred, Sheldon decides to create his own social group at his apartment and invites over Barry Kripke, Zack, Penny's ex, Stuart, the comic book store owner and Levar Burton, from TV's Reading Rainbow. Barry, Zack and Stuart all show up for various reasons of their own but Stuart and Barry soon become enamored with Zack's stories of getting girls and Sheldon quickly abandons them.

Meanwhile, the gang is hanging out a Raj's having chili con carne, laughing about what Sheldon would say if he was there. They soon discover that they actually miss his presence. Sheldon soon shows up, having left his newly formed group and says everything they all thought he would say. This time, though, rather than being annoyed, the gang encourages his criticism.

Amy and Bernadette kidnap Penny for a girls' night out to help her get over Leonard and his new relationship with Priya. Initially Penny is resistant to meeting anyone, but after Amy's incessant prodding, Penny decides that a one night stand may be just the thing for her.