Leonard: Good afternoon, Penny. So, hi, hey. Uh, I was wondering if you had plans for dinner.
Penny: Uh, do you mean dinner tonight?
Leonard: There is an inherent ambiguity in the word dinner. Technically it refers to the largest meal of the day whenever it is consumed, so, to clarify here, by dinner I mean supper.
Penny: Supper?
Leonard: Or dinner. I was thinking six thirty, if you can go, or a different time.

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.