The Big Bang Theory Season 5 Episode 16
The Vacation Solution
Sheldon is forced to take a vacation and decides to spend it at Bernadette's biology lab. She gives him "easy" tasks to do and he doesn't take it well. But, when she gives him the opportunity to cut into a brain, he cuts his thumb and faints. He apologizes for his attitude and returns the next day. Howard finds out that Bernadette wants him to sign a pre-nup. He isn't happy about it, but considers it.