Leonard: So, this is nice. First time we've all gotten together to eat.
Amy (to Sheldon): You're right. He's a festival of humdrum chitchat.
Leonard: Okay, that's all I got. Howard, you're up.
Wolowitz: Um, tell us about your work, Amy.
Amy: I doubt you'd understand. Sheldon tells me you only have a master's degree.
Wolowitz: Raj, do you have any questions for Amy?

Leonard: Did you guys see the paper in the American Physics Journal on supersolids? It's pretty interesting. This guy's working from a hypothesis which ...
Raj: Spoiler alert! Spoiler alert!
Leonard: What?
Raj: Don't ruin it for me, man! I printed out a PDF to read on the potty.

Leonard: Amy is judgmental, sanctimonious, and frankly just obnoxious
Sheldon: So?
Leonard: So we already have you for all that.

Leonard: Penny, Steve Wozniack was one of the co-founders of Apple computer. He and Steve Jobs...
Penny: Yeah. I know who he is. I watch Dancing With the Stars.

Sheldon: I don't understand why you're not enjoying this. Together, in this car, with my enhanced capabilities, we're like 'Knight Rider.'
Leonard: Except, in Knight Rider, the car isn't a yammering sphincter.
Sheldon: You mock the sphincter, but, the sphincter is a class of muscle without which human beings couldn't survive. There are over 50 different sphincters in the human body. How many can you name?
Leonard: I was wrong. This is exactly like Knight Rider

Raj: You slipped and fell into a robot hand?
Wolowitz: Yes.
Raj: Penis first?
Wolowitz: Yes. Now help me!
Leonard: I'd suggest a lubricant, but I have a feeling you fell on some of that as well.

When you say mistake, do you mean a fortunate mistake like the discovery of penicillin?

Don't worry about the moon. We set our laser to "stun."

Sheldon: I should have brought an umbrella.
Leonard: What for? It's not gonna rain.
Sheldon: I know that, but with skin as fair as mine, moon burn is a real possibility.

Sheldon: Are you asking me or telling me?
Leonard: Telling you?

Sheldon: That's not an apology; that's simply an acknowledgment that I was right.
Leonard: Okay, I'm sorry.
Sheldon: There you go.

Leonard: Is that your dad?
Wolowitz: If she grows any more hair on her face, yes.

TBBT Quotes

Penny: Hey, Sheldon, did you change your Wi-Fi password again?
Sheldon: Yes, it's "Penny, get your own Wi-Fi." No spaces.

Sheldon: Why do you have the Chinese character for "soup" tattooed on your right buttock?
Penny: It's not "soup," it's "courage."
Sheldon: No it isn't. But I suppose it does take courage to demonstrate that kind of commitment to soup.
Penny: How'd you see it? You said you wouldn't look.
Sheldon: Sorry. As I told you, the hero always peeks.