Penny: What is this?
Leonard: Oh, careful. That's my original series Battlestar Galactica flight suit.
Penny: Oh, why didn't you wear it on Halloween?
Leonard: Because it's not a costume, it's a flight suit.

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: Penny. We are made of particles that have existed since the moment the universe began. I like to think those atoms traveled fourteen billion years through time and space to create us, so that we could be together and make each other whole.

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: Is this the stuff you want me to try on?
Penny: No this is the stuff I want you to throw out. Seriously, don't even give it to charity. You won't be helping anyone.

Sheldon: Just the latest copy of Applied Particle Physics Quarterly.
Penny: Oh, you know, that is so weird that yours came and mine didn't.

Leonard: You are not Isaac Newton.
Sheldon: No, no, that's true. Gravity would have been apparent to me without the apple.