Penny: Whats Sheldon's deal? Is it girls, guys, sock puppets?
Howard: We operate on the assumption that Sheldon has no deal. Though we have many theories about how he might reproduce. I'm an advocate of mitosis.
Penny: What?
Howard: I believe that one day Sheldon will eat an enormous amount of Thai food and spilt into two Sheldons.

Sheldon: I'm sorry, coffee's out of the question. When I moved to California I promised my mother that I wouldn't start doing drugs.

Sheldon: In Papua New Guinea, there's a tribe when a hunter flaunts his success to the rest of the village, they kill him and drive away evil spirits with a drum made of his skin. Superstitious nonsense, of course, but one can see their point.

Sheldon: Excuse me, Penny, but-
Leonard: Don't tell her.
Sheldon: We're playing Klingon Boggle.
Leonard: Aww!
Howard: What do you mean "Aww?" Like she didn't know we were nerds?

Sheldon: Leonard, you may be right. It appears that Penny secretly wants you in her life in a very intimate and carnal fashion.
Leonard: You really think so?
Sheldon: Of course not. Even in my sleep-deprived state, I've managed to pull off another one of my classic pranks. Bazinga!

Penny: No Shoes, No Shirt, No Sheldon.
Howard: I bet we could sell that sign all over Pasadena!

Stephanie: I don't see anything at all, Sheldon.
Sheldon: Well, you're the doctor, but I am constantly hearing this annoying sound.
Leonard: Me too.
Sheldon: Is it a high frequency whistle?
Leonard: No, it's more of a relentless, narcissistic drone.

Beverly Hofstadter: It might explain why the two of you have created an ersatz homosexual marriage to satisfy your need for intimacy.
Howard: Say what?

Sheldon: Is my hamburger medium-well?
Leonard: Yes.
Sheldon: Dill slices not sweet?
Leonard: Yes.
Sheldon: Individual relish packets?
Leonard: Yes.
Sheldon: Onion rings?
Leonard: Yes.
Sheldon: Extra-breading?
Leonard: I asked.
Sheldon: What did they say?
Leonard: No.
Sheldon: Did you protest?
Leonard: Yes.
Sheldon: Vociferously?
Leonard: No.
Sheldon: Well then what took you so long?

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: I would ask you to find some way to suppress your libido.
Penny: I could think about you.
Sheldon: Whatever works.

Wolowitz: Raj, there's no place for truth on the Internet.

Sheldon: Penny.
Penny: Yeah.
Sheldon: Thanks for letting me stay here.
Penny: Oh, you're welcome sweetie.
Sheldon: Okay, I'm sleepy now get out.

Sheldon: She calls me moon-pie because I'm nummy-nummy and she could just eat me up.

Penny: Leonard, and Howard, and Raj, they aren't like other guys. They're special.
Alicia: Okay, they're special, and?
Penny: Well let's see how can I explain this. Um. They don't know how to use their shields.
Alicia: Shields?
Penny: Yeah. You know like in Star Trek and you're in battle, and you raise the shields.
*Realizing what she said* Where the hell did that come from?