Susan: Well, fine, if everyone wants to make jokes about our problems, then I can, too. Knock, knock.
Who's there? Our family is an embarrassment.
Randall: That's not much of a joke.

Leonard: Penny, as a scientist, my job is to figure out why things happen. But I don't think I'll ever understand how someone like me could get to be with someone like you. You know maybe I don't need to understand it, I just need to be grateful. I love you, Penny.

Raj: Can we take a moment to discuss that I just lied to the government for you?
Howard: Yeah, I would not have done that for you.

Sheldon: Do you think your father's doing unspeakable things to my mother?
Leonard: No.
Sheldon: Are you saying that because the things are unspeakable?
Penny: Your parents are old. Anything unspeakable was finished by 9:30.