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.

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: 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.