Leonard: You are not a burden, and we want you to come back and stay with us.
Raj: But I also upset Sheldon, and he's not gonna want to come over if I'm there.
Penny: More reasons for you to stay.

Raj: [to Amy] If you were having Sheldon's baby, would you really want him in the room?
Penny: Yeah, if he's in the room when they're making the baby, I'll give you $10.

Sheldon: Woman, you are playing with forces beyond your ken.
Penny: Yeah, well your Ken can kiss my Barbie.

Leonard: If I take it off, Sheldon wins.
Penny: Sweetie, every night you don't kill him in his sleep, he wins.

Raj: I'm sorry, guys. Sheldon was upset, Leonard and Penny were fighting. I just wanted to go someplace where I wasn't causing problems.
Howard: (sighs) I'll say it again. India.

Sheldon: What if she's correct? Doesn't that say something troubling about us?
Amy: I don't know. I just think you're the kind of person who likes a contingency plan.
Sheldon: That is true. Did you know I figured out in which order I would eat all my friends in the event of an apocalypse?
Amy: You need to stop hanging out with your brain so much. It's not a good influence.

Penny: Well, it's like that science thing. For every action, you have a gigantic and annoying reaction.
Leonard: Just when I thought you couldn't get any hotter.