Leonard: There's no discernible butt print.
Penny: Oh, come on. (Sits and wiggles around) There, butt print.
Leonard: It's too small and perfect.
Penny: Thank you.
Leonard: You're welcome.

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.

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: My point is, while you're spending all this time on your own, building computers or practicing your cello, what you're really doing is becoming interesting. When people finally do notice you, they're gonna find someone a lot cooler than they thought. And for those of you that were popular in high school, it's over, sorry. Thank you. Congratulations.

Howard: [looking at his caller ID] Ooh, looks like I'm gonna have sex tonight. [answering phone] Hey, baby...
Penny: His right hand is calling him?

Penny: What are we gonna do?
Leonard: We? No, no, no. You had your chance to be "we" for like a year and a half now. Right now, you are you and you are screwed!

Leslie: Boy, your heart's racing. I must've really gotten you going.
Wolowitz: Well, it's partly you, partly my transient idiopathic arrhythmia.
Leslie: Sexy.