Howard: I did a stupid thing.
Leonard: Yeah, I guessed that.
Howard: It was the kind of thing that makes it kind of hard to face her now.
Leonard: That covers anything from farting in bed to killing a homeless guy. Oh my God, you ran over a hobo.

Leonard: What would you be if you were attached to another object by an inclined plane, wrapped helically around an axis?
Sheldon: Screwed?
Leonard: There you go.

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.

Sheldon: This song is never going to stop. Have you ever dealt with something so relentlessly irritating?
Leonard: That's a trick question, right?

Leonard: Sometimes your movements are so lifelike I forget you are not a real boy.

Raj: Oh, you're so arrogant. If you were a super hero your name would be Captain Arrogant. And do you know what your super power would be? Arrogance.

Sheldon: Oh, Penny. Penny.
Penny: What's up?
Sheldon: Nothing. I just wanted to make Raj stop talking.