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: Are you upset about something?
Leonard: What was your first clue?
Sheldon: Well, it was a number of things. First, the late hour, then you demeanor seems very low energy, plus your irritability.
Leonard: Yes, I'm upset!
Sheldon: Oh. I don't usually pick up on those things. Good for me.
Leonard: Yeah, good for you.
Sheldon: (walks away and then turns back) Oh, wait. Did you want to talk about what's bothering you?
Leonard: I don't know. Maybe.
Sheldon: Wow! I'm on fire tonight.

Sheldon: Well, well, well, if it isn't Wil Wheaton. The Green Goblin to my Spider-Man, the Pope Paul V to my Galileo, the Internet Explorer to my Firefox!

Sheldon: Interesting. Sex works even better than chocolate to modify behavior. I wonder if anyone else has stumbled onto that.

Leonard: I know what you're doing.
Sheldon: You do?
Leonard: You're using chocolate as a positive reinforcement for what you consider is a correct behavior!
Sheldon: Very good. Chocolate?

Sheldon: I believe I would like to alter the paradigm of our relationship.
Amy: I'm listening.
Sheldon: With the understanding that nothing changes what so ever - physical or otherwise, I would not object to us no longer characterizing you as not my girlfriend.
Amy: Interesting, now try it without the quadruple negative.

Sheldon: So, just to clarify, when you say three, do we stand up or do we pee?

Leonard: Relax, it's just a dirty sock.
Sheldon: How on earth can you say "dirty sock" and "relax" in the same sentence?

Amy: This is an easy one. You love this guy.
Sheldon: Me.
Amy: Come on. He's an under appreciated genius.
Sheldon: Still think it's me.
Amy: It's not you. Now think, there's a car named after him.
Sheldon: Of course there is. The Mini Cooper because it's me.
Amy: How about this? He's a poor man's Sheldon Cooper.
Sheldon: Oh, Tesla.

Penny: Do you want to stop? I know you have trouble with eye contact.
Sheldon: Well, you have a brown fleck in your right iris that looks like a Formula 1 race car, so I'm just concentrating on that. Plus it's easier around people I'm comfortable with.
Penny: Oh, sweetie, I'm comfortable around you, too.
Sheldon: Of course you are. I'm warm and soothing. I'm like a human bowl of tomato soup.

Sheldon: *After just being jailed, at the biggest guy in the cell who's sitting on a bench* That's my spot.

Amy's Mom: It's nice to meet you too Sheldon, I honestly didn't believe Amy when she told me she had a boyfriend.
Sheldon: I assure you, I am quite real and I'm having regular intercourse with your daughter.
Amy's Mom: What?
Sheldon: Oh yes, We're like wild animals in heat. It's a wonder neither of us has been hurt!
Amy's Mom: Amy? What is he saying?
Amy: You wanted me to have a boyfriend, mother, well here he is! Have to sign off now. My hunger for Sheldon is stirring in my loins.
Sheldon: Oh yes. It's time for me to make love to your daughter's vagina.

Sheldon: Penny, while I subscribe to the "Many Worlds" theory which posits the existence of an infinite number of Sheldons in an infinite number of universes, I assure you that in none of them am I dancing.
Penny: Are you fun in any of them?
Sheldon: The math would suggest that in a few I'm a clown made of candy. But I don't dance.

Penny: OK Sheldon, what can I get ya?
Sheldon: Alcohol.
Penny: Could you be a little more specific?
Sheldon: Ethyl alcohol, 40 millilitres.

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?