2x21 - The Vegas Renormalization • peb, filmweb, rapidshare, torrent

Leslie Winkle breaks up with Howard, and he becomes depressed. Leonard and Raj decide to take him on a trip to Las Vegas in order to cheer him up. While in Vegas, a prostitute named Mikaela (Jodi Lyn O'Keefe) begins talking to Raj. He and Leonard eventually decide to hire her to pose as a Jewish woman and seduce Howard. When Howard realizes what is going on, he thanks Leonard and Raj for setting up this "date."

Sheldon, who has declined to come on the trip to Vegas, is ready to spend the weekend alone. He returns home to find that he has forgotten his key inside his locked apartment. Since the building manager will not arrive until the next morning, and Penny says she left her emergency key in their apartment, he is forced to spend the night with her. He sleeps in Penny's bed because he can't fit on the couch. When Leonard returns at the end of the episode, Sheldon comes out of Penny's apartment, telling Leonard he had dinner with her and spent the night. He also tells him that he has a better understanding of the term "friends with benefits," (which was a question he had the entire episode) before entering the apartment, leaving a bewildered Leonard looking shocked.
The title refers to the process of "renormalizing" Howard (getting him back to his old self) by taking him to Las Vegas. Renormalization is a related mathematical procedure in theoretical physics.