Sheldon: What computer do you have? And please don't say a white one.

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: 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: I am uncomfortable having been included in your lie to Penny.
Leonard: What was I supposed to say?
Sheldon: You could have told her the truth.
Leonard: I could not have said that, it would have hurt her feelings.
Sheldon: Is that a relevant factor?
Leonard: Yes.
Sheldon: Then I suppose you could have agreed to go.
Leonard: What would I have said afterwards?
Sheldon: I would suggest something along the lines of "singing is neither an appropriate vocation nor avocation for you and if you disagree, I recommend you do a CAT scan to locate the tumor which is pressing on the cognitive processing center of your brain".

Leonard: When we watch Frosty the Snowman, he roots for the sun.
Sheldon: Excuse me, but the sun is essential for all life on earth. Frosty is merely a bit of frozen, supernatural ephemera in a stolen hat. A crime, by the way, for which he is never brought to account.

Store Clerk: Excuse me, Sir, you don't work here.
Sheldon: Yes, well apparently neither does anyone else.

Penny: Why are there tears?
Leonard: Everything's fine. We just started talking about living arrangements.
Amy: Are you crazy? You know he's a flight risk!
Sheldon: That's exactly what I told him.

Penny: Wait, what is wrong with you two? He was talking about television during their date night.
Sheldon: Oh, not just date night. Our 5th anniversary.
Penny: Okay, see, that's even dumber than you wondering if being bitten by a goat would give you the powers of a goat.
Sheldon: If that happens, don't make me wait ten years to watch you eat a tin can.

Penny: Well, what's the third option?
Sheldon: That I have coitus with her.
(Penny's wine glass smashes in her hand)

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

Sheldon: We no longer live at 2311 Los Robles. We live at 311 Los Robles. [holds up number 2 fixture]
Leonard: You changed the address on the building? What about mail?
Sheldon: No worries. I explained our predicament to our letter carrier. He was sympathetic. His exact words were, "Got your back, Jack. Bitches be crazy."

Sheldon: What exactly does that expression mean, 'friends with benefits?' Does he provide her with health insurance?

Sheldon: I am the ball, my thoughts are its thoughts, its holes are my holes.

Penny: What the hell's going on?
Sheldon: You hypocrite.
Penny: What?
Sheldon: Little Miss Grown-Ups-Don't-Play-With-Toys! If I went into that apartment right now, would I not find Beanie Babies? Are you not an accumulator of Care Bears and My Little Ponies? And who is that Japanese feline I see frolicking on your shorts? Hello, Hello Kitty!

Sheldon: Under normal circumstances I'd say I told you so. But, as I have told you so with such vehemence and frequency already, the phrase has lost all meaning. Therefore, I will be replacing it with the phrase, "I have informed you thusly".