Leonard: Okay, I have just one question for you. While I am perfectly happy with the way things are between us, you said that you didn't wanna go out with me because I was too smart for you. Well, news flash, lady: David Underhill is 10 times smarter than me. You'd have to drive a railroad spike into his head for me to beat him at checkers. Next to him, I'm one of those sign-language gorillas who knows how to ask for grapes. So my question is what's up with that?
Penny: (tearfully) Why are you yelling at me?
Leonard: Sorry, I'm sorry, I'm sorry. Never mind, we're cool.

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.

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.

Sheldon: All I need is a healthy ovum and I can grow my own Leonard Nimoy.
Penny: Okay, all I'm giving you is the napkin, Sheldon.

Penny: Now, honey, it's okay. You don't have to get me anything in return.
Sheldon: Of course I do. The essence of the custom is that I now have to go out and purchase for you a gift of commensurate value and representing the same perceived level of friendship as that represented by the gift you've given me. It's no wonder suicide rates skyrocket this time of year.
Penny: Okay, you know what? Forget it. I'm not giving you a present.
Sheldon: No, it's too late. I see it. That elf sticker says to Sheldon. The die has been cast, the moving finger has writ, Hannibal has crossed the Alps.

Sheldon: If I would give you this gift basket, based on that action alone and no other data, infer and describe the hypothetical relationship that exist between us.
Store Clerk: Excuse me?
Sheldon: Here. Now, are we friends? Colleagues? Lovers? Are you my grandmother?
Store Clerk: I don't understand what you're talking about and you're making me a little uncomfortable.
Howard: See? Sounds just like you and Penny. We'll take it.