Penny: Bug report: when a guy asks me to spend some time with him, maybe he plans something a little more interesting than hanging out at home and watching TV.
Leonard: Even Doctor Who?
Penny: Even Doctor Who.

Leonard: Two ten and you throw in the Iron Man helmet.
Stuart: Are you crazy? That helmet's signed by Robert Downey Jr.
Leonard: So?
Stuart: Okay, if you're going to question the importance of an actor's signature on a plastic helmet from a movie based on a comic book, then all of our lives have no meaning!

Bernadette: What are you going to get at the train store, Sheldon?
Sheldon: Oh, I'm not buying anything. They're having a lecture. H-O gauge railroading. Half the size of O-gauge, but twice the fun. Very controversial topic.
Howard: Which side do you come down on?
Sheldon: I'll let you know after tonight. Unlike some people, I'm going in with an open mind. Who am I kidding? Of course we all know it's O-gauge or no gauge.

Stephen Hawking: You made an arithmetic mistake on page 2.
It was quite a boner.

Raj: Oh, my goodness. Aren't you the cutest little Yorkie ever! You got him for me?
Howard: Her. We thought you two would hit it off.
Raj: I think we already have.

Mrs. Wolowitz: Make up all you want. Your tuchus is not leaving this planet.

Sheldon: Uh oh, hypothetical aftershock. (Sheldon grabs Leonard and pushes him over) And that's why we wear hard-hats.

Raj: That is one tough birdie.

Leonard: Penny and Leonard 2.0. We can test it internally, shake out the bugs, and if we both think it is solid, we roll it out to the public.

Leonard: Hey, how about if we pretend we're actually on a first date? See how that goes.
Penny: Okay.
Leonard: So, Polly, tell me about yourself.
Penny: It's Penny.
Leonard: Oh, sorry, yeah. Awkward.

Sheldon: Amy, the relationship agreement was not designed for either one of us to get our way.
Amy: You use it to get your way.
Sheldon: I use it to get the right way. The fact that the right way is also my way is a happy coincidence.

Howard: Someone has to go up with the telescope as a payload specialist and guess who that someone is.
Sheldon: Mohammed Lee.
Howard: Who's Mohammed Lee?
Sheldon: Mohammed is the most common first name in the world. Lee, the most common surname. As I didn't know the answer, I thought it gave me the mathematical edge.

Leonard: See that? I just saved us forty bucks.
Sheldon: I've long said what you lack in academic knowledge, you make up for in street smarts.

(After Sheldon passes out after the Halloween prank)
Howard: who had there money on faint?
Raj: I had pee his pants.
Leonard: Hang on, looks like everyone's a winner.

Penny: Amy, what's wrong?
Amy: My boyfriend's a jerk.
Penny: Well, I know he didn't cheat on you, so what happened?