Sheldon: What if the helium dealer rats us out? What if Kripke asks where we got it? What if the university checks my family tree and finds out I don't have an Uncle Harvey?
Leonard: The dealer doesn't care, Kripke has no authority over us, and you being related to a metal container would explain a lot.

Sheldon: I remember the song! It's called "Darlin'" by the Beach Boys! Oh, thank goodness! I'm not crazy! I don't have to take a pigeon as my bride!
Leonard: There goes our shot at him living on the roof.

Howard: Don't feel bad. Some day someone will be throwing out your work, too.
Leonard: That someone was Sheldon and the day was yesterday.

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?

Leonard: What are we going to do?
Sheldon: Perform the experiment immediately.
Leonard: I'd love to, but we need liquid helium and our shipment's on back order for a month.
Sheldon: A month? What? Are you kidding me? That would have been a good time for you to soften the blow.
Leonard: That shirt brings out the blue in your eyes.
Sheldon: Thank you. Aren't you sweet?

Sheldon: He has glasses and I'm a know-it-all. We are not built for prison.

Sheldon: Uh, but this is violating university code.
Leonard: A little, but if I may quote Einstein, "The pursuit of science calls us to ignore the rules set by man"
Sheldon: Huh. All right, do it. Tell him we're in.
Leonard: Done.
Sheldon: I can't find that quote on the Internet. Did you make that up?
Leonard: Before I answer, may I just say your skin has never looked better.
Sheldon: Aren't you just made of sugar.