Leonard: Howard, this is big science. You could be the engineer who builds the equipment that puts us on the cover of magazines.
Howard: I could also be the engineer who builds the crossbow that kills Sheldon.

Sheldon: *knock knock knock* Leonard? (x3)
Leonard: What, Sheldon!? What, Sheldon!? What, Sheldon!?
Sheldon: Tell me what you see here.
Leonard: The blunt instrument that will be the focus of my murder trial?

Howard: Hey, you want to make sure he gets nowhere with Penny without jeopardizing your friendship with either of them?
Leonard: I'm listening.
Howard: Just tell him to do everything you've done with her for the last two years.

Wolowitz: I'm a horny engineer, Leonard. I never joke about math or sex.

Sheldon: I wouldn't tell you the secret. Sssh!
Leonard: What secret? Tell me the secret.
Sheldon: Mom smokes in the car. Jesus is okay with it, but we can't tell dad.
Leonard: Not that secret, the other secret.
Sheldon: I'm Batman! Ssssh!

Sheldon: I still don't see why I need a driver's license. Albert Einstein never had a driver's license.
Howard: Yeah, but Albert Einstein didn't make me wet myself at 40 miles an hour.
Penny: Yeah, and I never wanted to kick Albert Einstein in the nuts.

Leonard: Penny, you don't want to get into it with Sheldon. The guy's one lab accident away from being a super villain.

(Sheldon smiles in a grotesque way).
Howard: Oh crap that's terrifying.

Wolowitz (watching America's Next Top Model): Oh, look! That's the future Mrs. Wolowitz. No, wait! That's the future Mrs. Wolowitz. With her head in the lap of... what a coincidence... it's the future Mrs. Wolowitz.
Leonard: Yeah, and they can all move in with you and your mother. The current Mrs. Wolowitz.

Raj: What do you say, Howard?
Howard: I say Vegas baby!
Raj: What are you gonna tell your mother?
Howard: Sea World baby!

Leonard: What were you doing at Penny's?
Sheldon: Well, we had dinner, played some games, and then I spent the night. Oh, and you'll be happy to know that I now have a much better understanding of 'friends with benefits.'

Mrs. Wolowitz Howard, there's a blonde girl, Patsy, here to see you.
Howard: Who?
Mrs. Wolowitz Okay, now she's saying it's Penny.

Sheldon: I often forget other people have limitations. It's so sad.
Howard: He can feel sadness?
Leonard: Not really. It's what you and I would call condescension.

Sheldon: All I need is a healthy ovum and I can grow my own Leonard Nimoy.
Penny: Okay, all I'm giving you is the napkin, Sheldon.

Penny: Whats Sheldon's deal? Is it girls, guys, sock puppets?
Howard: We operate on the assumption that Sheldon has no deal. Though we have many theories about how he might reproduce. I'm an advocate of mitosis.
Penny: What?
Howard: I believe that one day Sheldon will eat an enormous amount of Thai food and spilt into two Sheldons.