Amy: Are you in the lanthanide series?
Sheldon: Amy, it's Penny's turn. Penny.
Penny: Uh, I dunno. Are you food?
Sheldon: That's not a apropos! We've already established I'm found on the Periodic Table.
Penny: Well, it's a table, right? I mean, why can't there be food on it?
Sheldon: I knew she wasn't lead car material.

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

Leonard: Come on! We have a combined IQ of 360 we should be able to figure out how to get into a stupid building.
*Two girls selling cookies ring every bell, the door opens*
Sheldon: What do you think their combined IQ is?

Penny: Are you saying that Amy is, oh, what's the scientific word-
Sheldon: Forget science: she's horny.

Leonard: Okay, I know what you're doing.
Sheldon: Really?
Leonard: Yes, you're using chocolates as positive reinforcement for what you consider correct behavior.
Sheldon: Very good. Chocolate?
Leonard: No, I don't want any chocolate! Sheldon, you can't train my girlfriend like a lab rat.
Sheldon: Actually, it turns out I can.

Sheldon: There was a tall man from Cornwall. Whose length exceeded his bed. "My body fits on it. But barely upon it. There's no room for my big Cornish head!"

Sheldon: No cuts, no buts, no coconuts.

Sheldon: Well, this is very pleasant.
Leonard: I'm glad you're enjoying yourself.
Sheldon: And you said there would never be enough pasta for the three of us.

Stephen Hawking: What does Sheldon Cooper and a black hole have in common? They both suck.

Sheldon: All right, this goes against everything I stand for, but desperate times call for desperate measures. (Kneels down to pray) Lord, this is Sheldon Cooper, you're good friends with my mom. I know I've spent my life denying that you exist-
Howard: Got them!
Sheldon: -and I will continue do so!

Sheldon: 'He drank from Leonard`s glass' - the words they will be carving into my tombstone.

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

Sheldon: Hello, Penny. I realize you are currently in the mercy of your primitive biological urges. But, as you have an entire lifetime of poor decisions ahead of you, may I interrupt this one?

Sheldon: Leonard, when that woman moved in three years ago I told you not to talk to her, and now look. We're going to be late for the movies.

Penny: Sheldon, could I ask you a question?
Sheldon: I would prefer that you not, but I wouldn't go so far as to forbid it.