Penny: No, it does matter. Okay? You were right. It was Halloween. I was dressed as a cat, you were a hobbit. It was right there on that couch.
Leonard: Why didn't you just say that?
Penny: Because I always hated that was our first kiss. I was drunk, and I was still with Kurt, and I was using you to make myself feel better. I just wanted our first kiss to mean something. That's why I said it was the one on your birthday.
Leonard: I like that. We'll make that our official first kiss.

Leonard: What would you be if you were attached to another object by an inclined plane, wrapped helically around an axis?
Sheldon: Screwed?
Leonard: There you go.

Leonard: Penny, as a scientist, my job is to figure out why things happen. But I don't think I'll ever understand how someone like me could get to be with someone like you. You know maybe I don't need to understand it, I just need to be grateful. I love you, Penny.

Sheldon: This song is never going to stop. Have you ever dealt with something so relentlessly irritating?
Leonard: That's a trick question, right?

Amy: Hey, why aren't you in your costume?
Sheldon: I just didn't feel like it.
Amy: You get that I'm wearing a corset because of you, not because I'm tired of breathing?

Leonard: Oh, my God, you look amazing.
Raj: I find you guilty of murder, because you are killing it.
Howard: (imitating Sheldon) Well, technically, the Supreme Court wouldn't determine a defendant's guilt or innocence in a criminal matter. They could only reverse or revamp a jury's conviction based on a constitutional or statutory issue.

Howard: You're sitting in my spot.
Sheldon: You don't have a spot. What is wrong with you today?
Raj: Maybe he's cranky because he's off his bathroom schedule.