Leonard: Hang on. Are you feeling insecure? Because that's my thing, and if you take it away, I don't know what I'm bringing to this relationship.

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.

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: My point is, while you're spending all this time on your own, building computers or practicing your cello, what you're really doing is becoming interesting. When people finally do notice you, they're gonna find someone a lot cooler than they thought. And for those of you that were popular in high school, it's over, sorry. Thank you. Congratulations.

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

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.

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