Penny: What got you excited about dark matter in the first place?
Sheldon: Well, I left string theory, which I'd been working on for a long time, and everyone was talking about how cool dark matter was, and I thought, "€œWell, sure, I'll give that a whirl".
Penny: So it's your rebound science?
Sheldon: What's that?
Penny: Well, not the science you spend the rest of your life with, but the one you use to make yourself feel pretty again.

Penny: So it's sort of like a guitar string, but instead of making an actual sound, each vibration is a different particle?
Sheldon: Precisely. And when you express it in 11 dimensions, Einstein's relativity equations pop out. Does that sound like a coincidence?
Penny: It does not.

Penny: So, so, did we do it? Did we just solve string theory?
Sheldon: Oh. (laughs) I appreciate your enthusiasm, but this is not the sort of thing we can figure out in a night. People have been stuck on this for decades.
Penny: What, decades? Really? It's-it's a string. How hard can it be? It's straight, it's in a loop, it gets knotted up with other strings.
Sheldon: Well, actually there are no knots in anything greater than four dimensions. Ooh, unless we get around that by considering them as sheets. You know, topologically speaking, that has a lot of interesting possibilities.
Penny: See? How long did that take me, like a minute?

Penny: (pulling car over) Get out.
Sheldon: Well, I have to tell you that while I do have a theoretical understanding of the workings of an internal combustion engine, I'm not sure I'm capable of performing diagnostics.
Penny: I said, get out.
Sheldon: Okay. I'll give it a shot. (Penny drives away)

Leonard: Okay, now, what you want to do first is turn on the ignition and shift into drive.
Sheldon: I haven't fastened my seat belt yet.
Leonard: Okay, fasten your seat belt.
Sheldon: Click. Now, are there air bags?
Leonard: You don't need air bags.
Sheldon: What if a simulated van rear-ends me?
Penny: I'll hit you in the face with a pillow.

Leonard: And what are the side effects?
Penny: Oh, shoot, shoot.
Leonard: Mm, remember the mnemonic.
Penny: Ah. GRAVY, yes. G-R-A-V-Y. Okay, gastric distress, redness, anal leakage, vasculitis and yellow eyes.
Leonard: Oh, uh, so close. It's actually yellow discharge.
Penny: Oh, right. That's why we went with "gravy."

Penny: He knows he doesn't live here anymore, right?
Leonard: Maybe he's experiencing memory loss because he took...
Penny: Flaxitrite!
Leonard: Yeah.

Leonard: Uh, Sheldon, what are you doing?
Sheldon: Oh, I was just checking in on my old room to see what you've done with it.
Penny: Why?
Sheldon: Well, I could use a place to work in the evenings, and-
Leonard: No.
Sheldon: Well, it's just that there's not a lot of space in our apartment-
Penny: No.
Sheldon: Well, and I feel like Amy's been having-
Leonard: No.
Sheldon: And since you're not-
Penny: No.
Sheldon: It's-
Leonard: No.
Penny: (Sheldon starts to speak) No.
Leonard: That is our room now, and we're gonna turn it into a gym.
Sheldon: Do you really expect me to believe that?
Leonard: No.
Penny: No.

Leonard: (on the phone) The answer is still no. You can say we wouldn't know you're here, but we'd know. Because you'd be here! (groans)
Penny: So, who was that?

Sheldon: I need somewhere to work in the evenings. You have a space you aren't using. Just take a look at my proposal.
Penny: (groans) What is this?
Sheldon: A rental agreement. I will only use the room for work. I won't sleep here, I won't eat your food, I won't even use your bathroom.
Leonard: So you can just walk in any time of the day or night?
Penny: Well, he does that now. At least this way we'll get paid.

Penny: I can't wait to see who the killer is. Is it that Ilsa girl? She seems pretty mean.
Leonard: But adorably mean, like a baby lion?
Penny: No, regular mean, like a regular lion.

Bernadette: Speaking of which, he came by yesterday to show me his book.
Penny: Oh, and-and what did you think?
Bernadette: I liked it.
Penny: Really? The Ilsa character didn't bother you?
Bernadette: Oh, he was exaggerating. You're not really like that.
Penny: Well, I know I'm not like that. The character was based on you.
Bernadette: I don't know what to tell you. When I brought it up with Leonard, he said it was you.
Penny: Well, when I brought it up, he got all squirrelly and left the room. Son of a bitch.

Penny: God, can we please just say no longer seeing each other?
Sheldon: Well, we could if it were true. But as you live in the same building, you see each other all the time. The variable which has changed is the coitus.
Penny: Okay, here’s the protocol, you and I are still friends, and you stop saying coitus.

Sheldon: How did you get in here?
Penny: What do you mean? Leonard's a member.
Sheldon: You told me it was incredibly exclusive.
Leonard: Y-Yeah, look, about that, I lied.
Penny: Hey, wait, you told me it was exclusive, too.
Leonard: Mm-hmm. I avoided him and impressed you, all with the same lie.
Penny: Damn, Hofstadter, didn't think you had it in you.

Bernadette: Yeah, I just wanted to stop in and see my office before we went to lunch.
Penny: Just a few more weeks, you'll be back full-time, huh?
Bernadette: Yeah.
Penny: Uh-oh. That wasn't a happy "yeah." That was a "Hey, Leonard, do you want to go to the gym?" yeah.