Leonard: Hey, pretty lady.
Penny: Oh, you seem extra happy.
Leonard: Uh, I guess I am.
Penny: Any particular reason why?
Leonard: I don't know, just having a good day. This morning Sheldon fell asleep on the way to work, so I got to listen to the radio. That was pretty crazy.
Penny: Mm-hmm. Anything else?
Leonard: Mm. I found this quiz online called "Which Star Trek Character Are You?" and it only took me four tries to get Captain Kirk.

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?

Amy: I have a lab full of coked up monkeys with nothing to lose.

Alex: Is there a problem?
Sheldon: Let's not call it a problem. Let's call it an opportunity. To solve a serious problem.

Sheldon: My father used to say that a woman is like an egg salad sandwich on a warm Texas day.
Alex: What?
Sheldon: Full of eggs and only appealing for a short time.