Zack: So how's the science world? What are you guys up to?
Howard: We've actually been working on a prototype for a navigation system we invented.
Leonard: But we won't bore you with the details.
Zack: Are you kidding? I love science. Einstein, Stephen Hawking, Mike deGrasse Tyson.
Amy: Mike deGrasse Tyson?
Howard: Yeah, you know, the boxer who grew a mustache and became a scientist.

Howard: You know, I'm really glad you decided to learn Mandarin.
Sheldon: Why?
Howard: Once you're fluent, you'll have a billion more people to annoy instead of me.

Josh: So, I have to ask, was the robot sexy?
Howard: It was actually just a mechanical hand.
Josh: 'Cause that's all you need, right?
Howard: You are my brother.

Sheldon: Sheldon Cooper does not cry.
Howard: That's true, you'd rust.

Sheldon: Well, it makes perfect sense. Because you're an expectant mother, you can't drink alcohol. I don't like to. You can't have sushi. I don't like to. You can't go in hot tubs. I consider them vats of sweaty people soup.
Bernadette: Gee, Sheldon, I dont know.
Sheldon: Oh, come on. Roller coasters, caffeine, runny eggs, I've been avoiding these things all my life. And now, because you're pregnant, you have to.

Leonard: Hey, did you ever think about the military applications for the guidance system?
Sheldon: Of course.
Leonard: Does it bother you?
Sheldon: No, it did at first. But then I talked it through with Frank and Alicia, and they really helped put things into perspective.
Leonard: Who are these people?
Sheldon: Leonard, friends are like toilet paper. It's good to have extras under the sink.

Raj: Hey, dude, you're killing me with Claire.
Zack: What are you talking about?
Raj: I mean, come on, look at you. You're classically handsome, you've got a swimmer's body. Next to you, I look like me.