Season 5: Episode 16 - The Vacation Solution

The Vacation Solution: ­Sheldon is forced to use his two weeks of vacation time from work, so he goes to work with Amy in her biology lab. He feels the tasks she asks him to do are menial and boring, but when she finally relents and asks him to dissect a brain, he cuts his thumb and passes out from the pressure. Bernadette wants Wolowitz to sign a pre-nup before their wedding, so Penny asks Leonard to try and get his feelings on the subject.