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

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

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?

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!

I think that you have as much of a chance of having a sexual relationship with Penny as the Hubble telescope does of discovering at the center of every black hole is a little man with a flashlight searching for a circuit breaker.

There's always a chance that alcohol and poor judgment on her part may lead to a wonderful evening

Leonard: No, I'm done with Penny. I'm going to be more realistic and go after someone my own speed.
Raj: Like who?
Leonard: I don't know... Olivia Geiger?
Sheldon: The dietitian at the cafeteria with the limp and lazy eye?
Leonard: Yes.
Sheldon: Well, I don't think you have a shot there

Sheldon: I have noted that Leslie Winkle recently started shaving her legs. Now, given that winter is coming, one can only assume that she's signaling sexual availability.
Wolowitz: I don't know. You guys work in the same lab.
Leonard: So?
Wolowitz: There are pitfalls. Trust me, I know. When it comes to sexual harassment law, I'm a bit of a self-taught expert.
Leonard: Look Howard, if I were to ask Leslie Winkle out, it would just be for dinner. I'm not going to walk into the lab, ask her to strip naked and dance for me.
Wolowitz: Oh, then you're probably okay

Sheldon: I couldn't sleep knowing that just outside my bedroom is our living room and just outside our living room is that hallway and immediately adjacent to that hallway is this! (showing Penny's messed up apartment)
Leonard: Do you realize if Penny wakes up there's no reasonable explanation to why we are here?
Sheldon: I just gave you a reasonable explanation.
Leonard: No, no. You gave me an explanation. Its reasonableness will be determined by a jury of your peers

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?