Sheldon: Wait, hold on, hold on. How do we know that you're not gonna take the money and drive away?
Leonard: What ya doing, Skippy?
Sheldon: Exactly what 1970s television crime dramas have taught us.
You give us the helium first.
Dealer: Oh, how do I know you're not gonna drive away without paying me?
Sheldon: Guess I'm not the only one who watches '70s television crime dramas.

Dealer: Huh. All these years, I've been using stalemate, when I really mean impasse. I feel foolish.
Leonard: I don't think it matters if this is a stalemate or an impasse or a Mexican standoff. What are we gonna do here?
Dealer: Oh, whoa, whoa, how can it be a Mexican standoff? Everybody knows you need three sides for that.
Sheldon: Not necessarily. Uh, many argue the essence of a Mexican standoff is that no one can walk away from the conflict without incurring harm.
Dealer: Hmm, I don't follow.
Sheldon: Let me give you an example. Earlier today, I decoded the headers on your e-mail, and I know that your name is Kenneth Fitzgerald.
From that, I figured out where you live and where you work.
Now, to make this a Mexican standoff, I would say something like, uh, "You give us the helium or I'll turn you in to the authorities."
Dealer: Is that a threat?
Sheldon: Yeah, exactly. See, you're getting it.
Dealer: Yeah, well, I know where you work, all right? And if you mess with me, I'll report you, then I'll pound your asses into the ground.
Sheldon: Perfect! Now we really are in a Mexican stand-off.

Bernadette: Ew, check out his tiny teeth. He looks like a man-dolphin.
Penny: Wait, if he's good in bed, she can throw him a fish.
Howard: (high-pitched) I love you, Amy. (dolphin sounds)

Sheldon: What if the helium dealer rats us out? What if Kripke asks where we got it? What if the university checks my family tree and finds out I don't have an Uncle Harvey?
Leonard: The dealer doesn't care, Kripke has no authority over us, and you being related to a metal container would explain a lot.

Amy: It's going fine. It's mostly just been meeting people for coffee.
Raj: Wha?!
I thought we were all- Never mind.

Leonard: Can you give us a minute?
Barry Kripke: Take your time. I'll walk out backwards for dramatic effect.

Leonard: Uh, I'm Leonard. This is my friend-
Sheldon: I'm Skippy. Skippy Cavanaugh.

Sheldon: Is this one of those times where I've won the battle but lost the war?
Leonard: Afraid so, Skippy.
Sheldon: I told you we shouldn't go shopping at night.

Penny: Where do we stand on cross-eyed Mike?
Raj: You know he won't be looking at other girls.
Howard: Unless they're sitting on the end of his nose.

Sheldon: Right this way, Uncle Harvey.
Leonard: Will you stop with that already?
Sheldon: I'm trying not to attract attention.
Leonard: And tipping his hat to the cleaning lady didn't do that?
Sheldon: She said, "Buenas noches." What was he supposed to do?