Penny: Okay, well, you know, it's just me. I'm still getting over this break-up with Kurt, and this thing with Doug would be just rebound sex.
Leonard: Ugh, don't get me started on rebound sex.
Penny: It's just, it's my pattern. I break up, then I find some cute guy, and then it's just thirty six meaningless of ... well, you know.
Leonard: I'm not sure that I do. Um, is that one thirty-six hour experience, or is it thirty six hours spread out over say, one ... glorious summer.
Penny: No, it's usually over a weekend, and trust me, you do not feel good after it.
Leonard: Well, chafing, right?
Penny: Emotionally.
Leonard: Of course, yeah, emotional chafing.

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.

Howard: Sheldon, if you were a robot and I knew and you didn't, would you want me to tell you?
Sheldon: That depends. When I learn that I'm a robot, will I be able to handle it?
Howard: Maybe, although the history of science fiction is not on your side.

Sheldon: I think that you have as much of a chance of having a sexual relationship with Penny as the Hubble telescope does of discovering at the center of every black hole is a little man with a flashlight searching for a circuit breaker.

Sheldon: I do feel obligated to point out to you that she did not reject you, you did not ask her out.
Leonard: You're right. I didn't ask her out. I should ask her out.
Sheldon: No! No that was not my point. My point was don't buy a cat.
Leonard: No, but you're right, I should march over there and ask her out.
Sheldon: Oh, goody! We're getting a cat.