Leonard: I have asthma. Back off!

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: [to Raj] Run to India.

Amy: As my mom used to say, "When you're doing a puzzle, it's like you've got a thousand friends." She was full of fun lies like that.

Sheldon: My brain is better than everybody's!