Sheldon: Stephen Hawking is a genius. If he said 'no,' I wasn't going to waste time on her father.

Sheldon: You know what? Let me give you a better question. Here, um, "Dr. Cooper, "I heard you were working on a top-secret project "for the U.S. military. Why don't you tell us about that?" See, that's a great question.
Dr. Harris: Okay, what was that like?
Sheldon: Oh, I can't tell you that, it's top-secret.

Sheldon: Hello?
Leonard: Oh, hey, where you been? We've been calling you for hours.
Sheldon: Oh, I'm sorry, my phone was on "airplane" mode.
Leonard: Why?
Sheldon: Because I was on an airplane. (makes confused gesture to Amy)

Sheldon: Amy's upset? Is it about me?
Leonard: No, I think it's because we're eloping.
Sheldon: Your marriage is causing her pain? You know great, I take it back. Go ahead and do it. Yay for love!

Leonard: Maybe you should consider women who aren't in serious relationships with your closest friends?
Sheldon: There's that prostate doctor, but I'm still mad at her.

Sheldon: So that's all this day was? A plan to butter me up before delivering bad news?
Leonard: Come on, buddy.
Sheldon: No, I thought we were friends. You asked for a sip of my Icee. If you had your own straw, I might've said yes.

Sheldon: I've just discovered I don't have enough room on my hard drive for a Linux partition, so you and I are going to perform a full backup, re-initialize and then re-install all my operating systems.

Sheldon: Studies are shown that performing tasks such as eating, talking on a cell phone or drinking coffee while driving reduces ones reaction time by the same factors as ounce of alcohol.

Penny: You know, they have a really nice bar over at the Olive Garden.
Sheldon: I don't like the Olive Garden. They treat me like family.

Raj: Oh, you bought cookies?
Sheldon: Yes, fig newtons. I was going to ask which scientist both helped to discover calculus and had a famous cookie named after him. And then after someone said Newton, I was going to tell them they're wrong. The cookies are named after a town in Massachusetts. And then I'd throw the cookies away.

Amy: Hello.
Sheldon: Hi.
Amy: Ready for the aquarium?
Sheldon: I am. You know, and in an effort to reduce awkwardness as we learn how to function as friends, I printed out a list of safe topics for polite conversation.
Amy: If that makes you more comfortable.
Sheldon: If there were a list of things that make me more comfortable, lists would be on the top of that list.

Amy: And this is Dr. Gundersen from Stockholm.
Sheldon: Ah, Sweden. Home of my favorite Muppet and second-favorite meatball.
*Dr. Gundersen and Amy look blankly at Sheldon*
Sheldon: Okay, the Nordic reputation for a lack of humor is well founded. Boy, is his name Gundersen or No-fun-dersen?

Sheldon: It turns out being sweet isn't enough to keep a girl these days. I blame Madonna.

Sheldon: Here comes the Embarrassment Express. It stops at Fraudville, Wonder-Blunder-Berg and Kansas City, because it's a hub.

Raj: Hey, Sheldon, guess what I've heard today.
Sheldon: I'd imagine you heard any number of things today. When you arrived at work, you undoubtedly heard: Hello, Raj; How are you, Raj; and given you're wearing a new sweater vest, you may have heard: "New Sweater Vest" and possible, though less likely "Nice Sweater Vest."