Amy: I guess I should have known what I was getting myself into.
Leonard: Don't beat yourself up. You've never lived with anyone before.
Amy: That's true.
Leonard: And you're starting out with Sheldon Cooper. That's like getting your first pet and having it be- I don't know. What's a kind of pet that ruins your life?

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.

Sheldon: My mother was at bible study. I walked in the house expecting to find it empty, and I heard a sound coming from my parents' bedroom. When I opened the door, I saw my father having relations with another woman.
Penny: Oh, that's awful!
Sheldon: I know. It's also why I never open a door without knocking three times. I mean, the first one's traditional, but two and three are for people to get their pants on.

Sheldon: Being with Amy has awoken the sexual creature within. When I see a pretty gal walking down the street, I think, "hubba hubba" like any other guy.
Penny: You kiss your mother with that mouth? 'Cause it's fine.

Bernadette: Uh, I left my phone downstairs!
Howard: Damn, so did I.
Bernadette: Wait, I have my iPad.
Howard: What are you going to do, e-mail 911?