CBS

Season 5: Episode 23 - The Launch Acceleration

The Launch Acceleration: When NASA informs an extremely nervous Wolowitz that he's being moved up to an earlier launch, he tries to use the wedding as an excuse not to go into space. However, the fact that he's an astronaut is the only thing Bernadette's father likes about him, so he reluctantly agrees to the earlier mission. Meanwhile, Amy tries to get Sheldon to take the next step in their relationship by overwhelming him with things he loves, thinking the attachments he's made to his favorite things might transfer over to her. Sheldon doesn't like what she's trying to do, but he can't deny that it's very effective. Penny finally agrees to sleep with Leonard again, but he accidentally asks her to marry him in the middle of the act and she freaks out. Her ultimate answer is no, but their relationship is largely unaffected.