THE BIG BANG THEORY Season 4 Episode 24 The Roommate Transmogrification Photos : "The Roommate Transmogrification" - When Bernadette receives her Ph.D., the guys take joy in reminding an emasculated Wolowitz that he is the only one in their group who isn't a doctor.  Meanwhile, Koothrappali becomes Sheldon's new roommate after hearing Leonard and Priya engaging in a "Star Trek" bedroom fantasy, on the fourth season finale of THE BIG BANG THEORY, Thursday, May 19 (8:00-8:31 PM, ET/PT) on the CBS Television Network.