Leonard: Hey, I was thinking, if you want to do a couples costume, we could paint ourselves green and be Hulk and She-Hulk. Or we could paint ourselves blue and go as Nightcrawler and Mystique.
Penny: Is there any scenario where we're not in full body paint?
Leonard: Yeah, if you want us to look like losers.

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.

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.

Penny: So, do you want to come?
Amy: No, thanks. I already live in a place all the nerds come to.

Raj: Oh, Double Stuf Oreos, I remember when I could afford you.

Sheldon: He also has a remarkable amount of credit card debt.
Howard: I thought your dad paid your cards.
Raj: I have a card for emergencies that I pay for myself.
Sheldon: What emergency happened at the L.A. Zoo?
Raj: That's a penguin I sponsor. They're losing their homes to global warming, and my car gets, like, seven miles a gallon, so I felt bad.