The Roommate Transmogrification
The Big Bang Theory Season 4 Episode 24 (05/19/11)
Bernadette finds out she is getting her PhD and was offered a high-paying job from a pharmaceutical company, which makes Howard uncomfortable.
Leonard and Priya play "Star Trek" in the bedroom, so Raj ends up staying in Leonard's bedroom.
Leonard and Raj decide to trade apartments, until Priya moves into her own place.
Priya's parents find out about her and Leonard's relationship after he overhears them discussing Priya's plan to return to India.
Raj and Penny drink a lot of wine and wake up in bed together. Penny gets caught by the other guys leaving the apartment disheveled.