Bernadette: Speaking of new careers, how are things going with dark matter, Sheldon?
Sheldon: Oh, I have to say it's the most exciting time in the history of the field.
Bernadette: Oh, what's going on?
Sheldon: I started doing it.

Sheldon: She watched it. I'm gonna get that girl back.
Amy: I only watched it because you emailed it to me with the subject line "This is gonna make you mad."
Sheldon: She was listening through the door. She wants me.

Sheldon: They're very different. Physics answers the question: what is the nature of the universe? Geology answers the question: you know, what'd I just trip over?

Sheldon: I'm clearly too evolved for driving.

Penny: Sheldon, have you ever told Amy what it was like for you growing up in Texas?
Sheldon: No.
Penny: Well, why don't you tell her?
Sheldon: All right. It was hell.

Sheldon: [jumps out of the sofa] Bazinga, punk. Now we're even!

Sheldon: (to Leonard, who has decided to give up on Penny) Well, at least now you can retrieve the black box from the twisted, smoldering wreckage that was once your fantasy of dating her and analyze the data so you don't crash into Geek Mountain again.

Sheldon: According to the inexplicably irritable nurse behind the desk, you'll be seen after the man who claims to be having a heart attack, but appears to be well enough to play Doodle Jump on his iPhone.

Sheldon: Leonard, as soon as we get home, I want to have coitus with Amy. [checks for Amy's reaction] Okay, she can't hear.

Raj: Look at that. You've known you're gonna be a father for less than a day and you're already stepping up.
Leonard: I'm telling you, you got this.
Howard: Maybe you're right.
Sheldon: Of course he's right. You and I both know how hard it is growing up without a father. That's why I'm confident you're gonna be the best dad you can be.
Howard: Thank you, Sheldon.
Sheldon: You're welcome. And if he has twins, we can do all kinds of neat experiments on them.

Sheldon: Hello, I know you're out there. I can hear you metabolizing oxygen and expelling carbon dioxide.

Leonard: Sheldon, you need to find a better way of dealing with Penny.
Sheldon: What am I supposed to do? Eat French Toast on a Monday? Now that would be impossible.

Sheldon: You want me to use my intelligence in a tawdry competition? Would you ask Picasso to play Pictionary? Would you ask Noah Webster to play Boggle? Would you ask Jacques Cousteau to play Go Fish?

Sheldon: Do those sound like castanets to you?
Leonard: The box says 'kitchen'.
Sheldon: So? Do cocaine smugglers write 'cocaine' on the box?

Sheldon: Now to the astronomers in the audience, get ready to see the dark side of the moon. Now here's Uranus!