The Big Bang Theory Season 2 - Episode 2

"The Codpiece Topology"

The guys return from a Renaissance Fair and see Penny with a new guy, Eric (Travis Schuldt), prompting a jealous Leonard to pursue a relationship with fellow physicist Leslie Winkle. All the guys as well as Leslie humiliate Leonard for his apparent failure to keep Penny.

Leslie eventually agrees to date Leonard who convinces Sheldon to leave the apartment, to give his roommate and Leslie some privacy. On the staircase, while playing Super Mario 64, Sheldon explains to Penny that he feels uncomfortable with Leonard dating his arch enemy, Leslie, who is a "sloppy, arrogant, sub-par scientist".

Sheldon returns to their apartment and formally approves the relationship between Leonard and Leslie, graciously overlooking that she actually believes loop quantum gravity instead of string theory. Leslie gets emotional and makes statements about Lorentz invariance and black hole entropy which Sheldon scoffs at. Leslie expects Leonard to back up her beliefs but finds that he shares Sheldon's instead. Leslie then asks how they should raise the children as if it were a decision to raise their children in one religion or another. After learning about this "deal breaker" which she believes is more serious than Leonard's food allergy and shortness, she breaks up with Leonard. After which Sheldon tells Leonard to look on the bright side Leonard then replies with "What's the bright side?" Sheldon states that it is only 9 more months to Comic-Con. (In this episode it is revealed that at Comic-Con Raj made out with an attractive man dressed as a Green Orion Slave Girl.)
The title refers to Sheldon's complaint that the Renaissance Fair was more of a "medieval, slash Age of Enlightenment, slash any-excuse-to-wear-a-codpiece fair!"