Penny: Leonard might be home, can we talk in my apartment?
Sheldon: We're not done?
Penny: No!
Sheldon: Eh, why not? We're already through the looking glass anyway.

Sheldon: You know, I've been thinking about time travel again.
Leonard: Why, did you hit a roadblock with invisibility?
Sheldon: Put it on the back burner.

Penny: I need some guinea pigs.
Sheldon: Okay, there's a lab animal supply company in Reseda you can try. But if your research is going to have human applications, may I suggest white mice? Their brain chemistry is far closer to ours.
Penny: I swear to God, Sheldon, one day I'm going to get the hang of talking to you.
Leonard: His mom's been saying that for years.

Leonard: He sounds like a wise man.
Mary Cooper: Oh, not that wise. He once tried to fight a bobcat for some licorice.

Sheldon: Look, you may have democracy in your beloved Russia, but on this physics bowl team, I rule with an iron fist. (Raising his fist) Ow!

Howard: We'll just have to face Sheldon mano y mano y mano a mano.
Leslie: Wait, you're going up against Sheldon Cooper?
Howard: Yes!
Leslie: That arrogant, misogynistic, East Texas doorknob that told me I should abandon my work with high-energy particles for laundry and child bearing?
Leonard: She's in!

Sheldon: Yeah, I apologize for my earlier outburst! Who needs Halo when we can be regaled delightfully with the folksy tale of the "whore of Omaha"?

Mrs. Koothrappali: You are wearing the boxers we sent you, Rajesh?
Raj: Yes!
Mrs. Koothrappali: Because you know what happens to the samosas when you wear the tighty-whities.
Raj: Can we please stop talking about my testicles?

Sheldon: Tell Mom that I currently weigh 165 pounds and that I'm having regular bowel movements.

Sheldon: Explain to me an organizational system where a tray of flatware on a couch is valid. I'm just inferring that this is a couch, because the evidence suggests the coffee table's having a tiny garage sale.

Leonard: Come on, you need a four-person team. We're four people
Sheldon: By that reasoning we should also play bridge, hold up a huppah and enter the Olympic bobsled competition.

Penny: You'll never guess what just happened.
Leonard: Oh, I give up.
Sheldon: I don't guess. As a scientist, I reach conclusions based on observations and experimentation. Although it occurs to me, you may have been employing a rhetorical device rendering my response moot.

Howard: He compared Sheldon to a disposable feminine cleansing product one might use on a Summer's Eve.
Penny: Yeah and the bag it came in.

Penny: I'm so sorry. I really thought if you guys went instead of me, he wouldn't be such an ass.
Leonard: No, it was a valid hypothesis.
Sheldon: "Was a valid hypo-" . What is happening to you?

Sheldon: Can't we just go to Big Boy? They only have one burger: the Big Boy.
Penny: The Barbecue Burger is like the Big Boy.
Sheldon: Excuse me, in a world that already includes a Big Boy, why would I settle for something that's like a Big Boy?