Sheldon: I shower twice a day and wash my hands as often as I can.
Lalita: Really? So do I!
Raj: But you're a dentist, he's nuts

Sheldon: You are the living embodiment of the beautiful Princess Panchali.
Lalita: Oh, no kidding? Who is that?
Sheldon: A beloved character from an Indian folktale.
Lalita: Oh. "Us" Indian or "Come to our casino" Indian?
Sheldon: "You" Indian

Sheldon: When I was a little boy and got sick, which was most of the time, my mother would read [The Monkey and the Princess] to me. It's about an Indian princess who befriends a monkey who was mocked by all the other monkeys because he was different. For some reason I related to it quite strongly.
Penny: I know the reason.
Leonard: We all know the reason

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

Sheldon: I'll have a diet Coke.
Penny: Can you please order a cocktail? I need to practice mixing drinks.
Sheldon: Fine... I'll have a virgin Cuba Libre.
Penny: That's... rum and Coke without the rum.
Sheldon: Yes, and would you make it diet?

Leonard: Do you really need the Honorary Justice League of America Membership card?
Sheldon: It's been in every wallet I owned since I was five.
Leonard: Why?
Sheldon: It says keep this on your person at all times. It's right here under Batman's signature.

Penny: Hey, if you guys need a fourth, I'll play.
Leonard: Great idea!
Sheldon: Uh, no. The wheel was a great idea. Relativity was a great idea. This is a notion, and a rather sucky one at that.
Penny: Why?!
Sheldon: Why? Oho, Penny, Penny, Penny.
Penny: Oho, what, what, what? [picks up controller]
Sheldon: This is a complex battle simulation with a steep learning curve. There are a myriad of weapons, vehicles, and strategies to master, and not to mention an extremely intricate back story.
Penny: Oh, cool! Whose head did I just blow off?
Sheldon: Mine.

Leonard: You have a TV in your room. Why don't you just have breakfast in bed?
Sheldon: Because I am neither an invalid nor a woman celebrating Mother's Day

Leonard: Sheldon, think this through, you're going to ask him to choose between sex and Halo.
Sheldon: No, I'm going to ask him to choose between sex and Halo 3. As far as I know, sex has not been upgraded to include high-def graphics and enhanced weapons systems.
Leonard: You're right. All sex has is nudity, orgasms, and human contact.
Sheldon: My point

I don't know how, but she is cheating! Nobody can be that attractive and this skilled at a videogame

Sheldon: Who told you you could touch my board?
Leslie: No one.
Sheldon: I don't come in to your house and touch your board.
Leslie: There are no incorrect equations on my board.
Sheldon: Oh! That is so, so...
Leslie: I'm sorry; I've got to run, if you come up with an adjective text me.
Sheldon: Inconsiderate, that is the adjective, inconsiderate!

Penny: What's the matter?
Sheldon [confused by Leonard having Leslie in his room]: I don't know what the protocol is here. Do I stay? Do I leave? Do I wait to greet them with a refreshing beverage?
Penny: Gee, Sheldon, you're asking the wrong girl. I'm usually on the other side of the tie.

TBBT Quotes

Oh, Bernadette, please play my clarinet.

Raj's poem

Sheldon: I'll have a diet Coke.
Penny: Can you please order a cocktail? I need to practice mixing drinks.
Sheldon: Fine... I'll have a virgin Cuba Libre.
Penny: That's... rum and Coke without the rum.
Sheldon: Yes, and would you make it diet?