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.

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, 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.

Sheldon: This song is never going to stop. Have you ever dealt with something so relentlessly irritating?
Leonard: That's a trick question, right?

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.

Howard: All Ma's food is going to be ruined.
Bernadette: Why don't we take it home and put it on our freezer?
Raj: You don't want to do that. Refreezing not only removes moisture, but it creates ice crystals in the fibres of the meat that can compromise its taste and texture. What? I saw a teachable moment. I dropped some culinary science.