(Sheldon notices Penny taking Leonard to his bedroom)
Sheldon: What's going on?
Penny: Get your noise-cancelling headphones, 'cause it's gonna get loud.
Sheldon: Oh, not this again.

Wil Wheaton: What's wrong with him?
Stuart: Everybody has a different theory.

Leonard: Can I have a napkin.
Sheldon: I'm sorry, no!
Leonard: But you have a whole bunch of napkins.
Sheldon: Yes, I've moved to a four napkin system, lap, hands, face, and personal emergency. If you like, starting tomorrow, I'll add a guest napkin but I'm afraid there's nothing I can do for you today.
*Leonard grabs a napkin.*
Sheldon: Good luck, that's the face napkin.

Beverly Hofstadter: So, Howard, have you and Rajesh finally summoned the courage to express your latent homosexual feelings towards one another?

Leonard: Hey, where've you been?
Sheldon: I was talking with Penny.
Howard: What's wrong with you? You can't hang out with your roommate's ex. That's totally uncool.
Leonard: No, it's fine. I don't care. I'm over it.
Raj: Yeah, he's over it; that's why he's been whining all day about trying to invent that memory-wiper gizmo from Men in Black.
Sheldon: Is he making any progress? Because I'd like to erase Ben Affleck as Daredevil.
Howard: So would Ben Affleck.

Sheldon: I do not have to urinate. I am the master of my own bladder. Drat.

Sheldon: What are they doing here?
Leonard: We came to apologize again and bring you home. So why don't you pack up your stuff, and we'll head back?
Sheldon: No, this is my home now. Thanks to you, my career is over, and I will spend the rest of my life here in Texas trying to teach evolution to creationists.
Mary Cooper: You watch your mouth, Shelly. Everyone's entitled to their opinion.
Sheldon: But evolution is not opinion, it's a fact.
Mary Cooper: And that is your opinion.

Sheldon: Biologically speaking, Howard is perfectly justified in seeking out the optimum mate for the propagation of his genetic line. Howard: Thank you, Sheldon. Sheldon: And whether that propagation is in the interest of humanity is, of course, an entirely different question.

Howard: I have a two-part question.
Sheldon: Go ahead.
Howard: A: Are you kidding? And B: Seriously, are you freaking kidding me?
Sheldon: A: I rarely kid, and B: when I do kid, you will know it by my use of the word "Bazinga".
Howard: So you're saying the two of you are going to be sleeping in the same bed?
Sheldon: Yes. Bazinga.

Sheldon: I grew up in Texas. Football is ubiquitous in Texas. Pro football, college football, high school football, pee wee football - in fact, every form of football except the original, European football, which most Texans believe to be a commie plot.

Penny: Damn you, you rat bastard! In the olden days, I never would have known he was that stupid.

Sheldon: Excuse me. Wolverine Origin, mini series issue two, page 22, retractable bone claws. You know, if you three spent less time thinking about sex and more time concentrating on comic books, we would have much less of these embarrassing moments.

Raj: I'm going to be deported. Sent home in disgrace. Exposed to the sardonic barbs of my cousin Sanjay or, as you may know him, Dave from AT&T customer service.

Raj: Sorry doesn't make up for the fact that I had to cook chicken and rice with this vegan guy. You know what vegan chicken and rice is? It's rice!

Rajesh: Okay, please don't take this the wrong way, but I'd rather swim buck naked across the Ganges with a paper cut on my nipple and die a slow agonizing death from a viral infection, than work with you.