Leonard: He always needs all the attention. He's such a baby.
Penny: I know. I know.
Leonard: I swear he is never playing with my helicopter.

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: 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.

Professor Proton: Can I ask you a question?
Leonard: Yeah, sure.
Professor Proton: Why do you put up with Sheldon?
Leonard: Oh, you know because we're friends.
Professor Proton: Why?
Leonard: Wow, you ask really hard questions. Look, I know he can be aggravating, but what you have to remember is he's not doing it on purpose, it's just how he is. But he's also loyal and trustworthy and we have fun together.
Professor Proton: You know you're describing a dog?
Leonard: He did bite me once. But in his defense, I came up behind him while he was eating.
Professor Proton: They hate that.
Leonard: Sheldon is the smartest person I have met. He's a little broken and he needs me. And I guess I need him too.
Professor Proton: Why is that?
Leonard: Boy, you will not let this go, will you?

Penny: I mean, who even reads Scientific American?
Leonard: It's kind of a big deal.
Penny: If it's such a big deal, how come the biggest celebrity they could get for the cover is a molecule?

Penny: Wow, it looks really pretty in here.
Stuart: Yeah, turns out half a dozen Menorahs really sets a mood.

Sheldon: Is it my fault I have a much bigger reputation than he does?
Amy: It's not your fault.
Sheldon: Is it my fault that my name came first on the paper alphabetically?
Amy: Not your fault.
Sheldon: Is it my fault that when the reporter cited me as the lead scientist, I didn't correct him?
Amy: Hey look at that pretty bird.