Penny: Okay, listen, there's something I need to tell you. I've been thinking about going back to school for a while now. So a couple months ago, I started taking a history class at the community college.
Leonard: Oh. That's great. Great, great, great. Why wait so long to tell me?
Penny: I don't want you to make a big deal out of it.
Leonard: Why do you think I'd be like that? I get it, you're taking one class. It's nice. Maybe if it goes well, you take another, you enroll full-time. Ooh, be sure to keep an eye on which credits transfer to a four-year college.
Penny: You're making it a big deal.
Leonard: Sorry. (nonchalantly) Whatever. It's all good.

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.

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: 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.

Leonard: I did a bad thing.
Sheldon: Does it affect me?
Leonard: No.
Sheldon: Then suffer in silence.

Stephen Hawking: What does Sheldon Cooper and a black hole have in common? They both suck.

Sheldon: Steven Hawking's a genius and he talks like a robot. It's everything I ever wanted in a friend.