Sheldon: I must say, Howard, I think a detailed letter to MIT describing your current circumstances might entitle you to a refund on your master's degree.

Howard: Ok, now, this is an exact duplicate of The Wolowitz Solid Waste Disposal System, as deployed on the International Space Station.
Raj: Don't you mean the Wolowitz Solid Waste Distribution System?

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.

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.

Sheldon: For what it's worth, my mother says that when we deceive for personal gain, we make Jesus cry.

Sheldon: Why does Leonard get to go?
Wolowitz: Because he's upset over his situation with Penny, and if I have to hear about it again, I'm gonna kick him in his ovaries!
Leonard: Thanks for understanding.
Howard: I've got your back, sister!

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

Stuart: Uh, hey, Leonard, can I talk to you about something?
Leonard: Oh, sure, what's up?
Stuart: Remember I went out with your friend Penny a couple weeks ago?
Leonard: Yeah, vaguely.
Raj: Sure you remember. You went to the bar and made a fool of yourself trying to pick up strange women.

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.

Raj: Howard, wait. Why don't you use this instead of the PVC to keep the transverse filter assembly in place?
Howard: Because this is not a spare part from the space station. This is the thing from the pizza box that keeps the lid from touching the cheese.
Raj: That what that's for? In India, the lid just touches the cheese. Of course, we also have rampant poverty and periodic outbreaks of cholera, so a little cardboard in our cheese is no biggie.

Leonard: Thanks for closed captioning my pain, Raj.

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

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.

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