Howard: Hope you don't mind, I told my girlfriend, Bernadette, she can join us for dinner.
Leonard: Sure, the more the merrier.
Sheldon: Wait, no. That's a false equivalency. More does not equal merry. If there was 2000 people in this apartment right now, would we be celebrating? No, we'd be suffocating.

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".

Sheldon: They called it the greatest thing since the Communist party. Although I'm pretty sure the Communist party made them say that. I like China. See, they know how to keep people in line.

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: Hey, Sheldon, did you change your Wi-Fi password again?
Sheldon: Yes, it's "Penny get your own Wi-Fi"; no spaces.

Sheldon: No cuts, no buts, no coconuts.

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.

Leonard: What's a dogapus?
Sheldon: A hybrid dog and octopus. Man's underwater best friend.
Leonard: There's someone working on that?
Sheldon: I was going to. I planned on giving it to myself for my 300th birthday.
Leonard: Wait a minute you hate dogs.
Sheldon: A dogapus can play fetch with eight balls; no one can hate that.

Sheldon: I'm not Sheldon. I'm the Flash. And now I'm going to the Grand Canyon to scream in frustration. *takes two quick steps* I'm back.

Sheldon: Do you want to hear an interesting thing about stairs?
Leonard: Not really!
Sheldon: If the height of a step is off by as little as two millimeters, most people will trip.
Leonard: I don't care. 2 millime--? That doesn't seem right.
Sheldon: It's true. I did a series of experiments when I was 12. My father broke his clavicle.
Leonard: Is that why they sent you to boarding school?
Sheldon: No. That was the result of my work with lasers.

Sheldon: Good morning everyone and welcome to "Science and Society". I'm Dr. Sheldon Cooper, BS, MS, MA, PhD and ScD. OMG, right?

Leonard: Do you think we can outrun him?
Sheldon: I don't need to outrun him, I just need to outrun you.

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!