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.

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?

Sheldon: I need your help in a matter of semiotics.
Penny: What?
Sheldon: Semiotics, the study of signs and symbols as a branch of the philosophy related to linguistics.
Penny: Okay, honey, I know you think you are explaining yourself, but you're really not

Penny: This is the best cobbler ever!
Mary: You know what the secret ingredient is?
Penny: Love?
Marry: Lard

Mary: Now, you listen here. I have being telling you since you were four years old, it's okay to be smarter than everybody but you can't go around pointing it out.
Sheldon: Why not?
Mary: Because people don't like it. You don't remember all the ass kickings you got from the neighbor kids. Now lets get cracking. Shower, shirt, shoes and let's shove off.
Sheldon: There wouldn't have been any ass kickings if that stupid death ray had worked

I made chicken. I hope it's not one of the animals that you people think is magic

Mary [to Raj]

Sheldon: This car weighs, let's say, 4,000 pounds. Now add 140 for me, 120 for you...
Penny: 120?!
Sheldon: Oh, I'm sorry. Did I insult you? Is your body mass somehow tied into your self-worth?

Leonard, the Lord never gives us more than we can handle. Thankfully, he blessed me with two other children who were dumb as soup

Mary

Wolowitz: Forgive me for being so bold, but I now see where Sheldon gets his smoldering good looks.
Mary: Honey, that ain't gonna work, but you keep trying.

Sheldon: I can't believe he fired me.
Leonard: Well, you did call him a "glorified high school science teacher whose last successful experiment was lighting his own farts."
Sheldon: In my defense, I prefaced that with, "with all due respect."

Sheldon: How was your date?
Leonard: Awesome!
Sheldon: Score one for liquor and poor judgment

Sheldon: I have got the Sword of Azeroth!
Leonard: Forget the sword, Sheldon. Help Raj.
Sheldon: There is no more Sheldon. I am the sword master!
Wolowitz: Leonard, look out!
Leonard: Damn it, Sheldon, we're dying here.
Sheldon: Goodbye, peasants.
Leonard: Bastard teleported!
Raj: He's selling the Sword of Azeroth on eBay.
Leonard: You betrayed us for money? Who are you?
Sheldon: I'm a rogue night elf. Don't you people read character descriptions? Wait, wait, wait... somebody just clicked Buy It Now.
Wolowitz: I am the sword master!

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?