Leonard: Oh. It's Stuart.
Sheldon: You're not going to answer it?
Leonard: He wants to talk about Penny. I don't want to talk about Penny.
Sheldon: You're making an assumption. Perhaps the comic book store is on fire, and he needs your assistance.
Leonard: Why would he call me?
Sheldon: We don't know. And if you don't answer the phone, we can't know.

Sheldon: Smell that? That's the smell of new comic books. Oh, yes!
Howard: They're on me today, boys.
Raj: You're paying? Have you been selling your sperm again?

Sheldon: Yeah, I have to say I thought the toilet humor would get less funny with repetition. Apparently there is no law of diminishing comedic returns with space poop.

Penny: Leonard, could you pass the soy sauce, please?
Leonard: I'm sorry, were you talking to me?
Penny: Yeah, I said Leonard.
Leonard: Yes, you did, didn't you?

Leonard: Hey, Stuart, I need to talk to you.
Stuart: Sure, what's up?
Leonard: I think I gave you bad advice about Penny, and I want to apologize.
Stuart: No, your advice was great.
Leonard: It was?
Stuart: Yeah, going slow really worked.
Leonard: You're kidding. Never worked for me.

Howard: Is that supposed to be funny?
Sheldon: I believe it is. The combination of the Star Trek reference and the play on words involving the double-meaning of the verb to go suggests that Leonard is humorously mocking your efforts in space plumbing.

Penny: Well, does it bother you, me going out with one of your friends? 'cause you know, you and me.
Leonard: No, no that's the past. I'm really more of a right now kind of guy. You know, living in the moment. Although I do have to live a little in the future, 'case, well, that's my job. Of course, my fondness for classic science fiction does draw my attention backwards, but those stories often take place in the future. In conclusion, no, it doesn't bother me.

Howard: Here's an approximation of the spare parts available on the Space Station. We gotta find a way, using nothing but this, to reinforce this so the waste material avoids the spinning turbine.
Raj: You mean so it doesn't hit the fan?

Howard: Okay make your little jokes, but out of the four of us, I'm the only one who's making real world contribution to science and technology.
Rajesh: He's right, this is an important achievement for two reasons. Number one and of course number two!

Stuart: Here, Sheldon, I pulled the new Hellboy for you. It's mind-blowing.
Sheldon: Excuse me. Spoiler alert.
Stuart: I didn't spoil anything.
Sheldon: You told me it's mind-blowing.So, my mind is going into it pre-blown. And once a mind is pre-blown, it cannot be re-blown.
Stuart: I'm sorry.
Sheldon: Said the Grinch to Christmas.

Howard: (talking on the phone) Yes, sir, I understand classified. We'll keep it all classified, no one has to know but you and me.
Penny: What's classified?
Leonard: Howard's space toilet. I'll tell you later.

Penny: Well, In that case, do you mind giving me some advice?
Leonard: About Stuart? Love to.
Penny: He's very shy, how do I make him feel more comfortable around me?
Leonard: Well, uh, first of all, don't underestimate the value of discomfort.
Penny: Really?
Leonard: Well, yeah, Stuart thrives under pressure, that's why he works in a comic book store.

Penny: What the hell is that?
Howard: Meatloaf.
Leonard: What was it doing on the ceiling?
Howard: That's classified.

Penny: Morning. What’s up?
Leonard: Nothing. We just pulled an all-nighter trying to fix a zero-gravity ... pasta maker.

Leonard: It must be hell inside your head.
Sheldon: At times.