Sheldon: Well, I can understand how that would make someone irritable.
Howard: Interesting fact: "irritable" comes from the Latin, "susceptible to anger."
Sheldon: Just because I used a word doesn't mean I want its etymology.
Howard: Interesting fact: "etymology" comes from the Greek word-

Leonard: Sheldon, he's being you. He's dressed as you for Halloween.
Sheldon: Oh. So you're not laughing at him. You're laughing at me.
Raj: We're not laughing at you. We're laughing with you.
Sheldon: But I'm not laughing.
Raj: Then the first one.

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?

Sheldon: Amy, do you think I'm always correcting other people?
Amy: No, not all the time. I mean, just last week, Penny ended a sentence with a preposition. You didn't even mention it.
Sheldon: True. I just waited until I got home and screamed into a pillow.

Amy: Is something bothering you?
Sheldon: Howard dressed up as me and imitated me, and everyone laughed.
Amy: Oh. Well, that must have felt terrible.
Sheldon: It did. I never realized my friends viewed me as an object of ridicule.
Amy: Oh, I don't think that's true.
Sheldon: They laughed, Amy. In a derisive way. Not in the instructive way I laugh at them when they're being stupid.

Leonard: Hey, happy Halloween.
Penny: Oh! Trick or treat.
Leonard: No. Sorry, you're not wearing a costume.
Penny: Yeah, I am. I'm a pharmaceutical sales rep.
Leonard: I'm gonna need more.
Penny: Okay, failed actress who traded constant rejection for a Christmas bonus and a dental plan?
Leonard: Go nuts.
Penny: Oh. I will.

Leonard: So, what are you wearing to the party? Sexy cat? Sexy nurse? Sexy zombie?
Penny: Why do girls' costumes have to be sexy but guys' costumes don't?
Leonard: (scoffs) Say that again with this helicopter on my head.
Penny: Very cute.

Leonard: Hey, do you remember what happened at that first Halloween party that you invited me to?
Penny: When I threw up in the pumpkin?
Leonard: More memorable than that.
Penny: Really? That was pretty impressive.
Leonard: We had our first kiss. On this very couch.
Penny: No, no, our first kiss was at your birthday. Remember? I threw you a party, you didn't make it, and I felt bad for you.
Leonard: No, no, it was on Halloween, and you felt bad for me.
Penny: If we're gonna go through every party where I felt bad for you, we're gonna be here awhile.

Penny: You're not mad at me, are you?
Leonard: No. Of course not. No, we just remember different things from that party. I remember falling in love, and you remember vomiting in a pumpkin.
Penny: I was, like, four feet away. People cheered.

Amy: Maybe Howard could apologize?
Bernadette: You're kidding, right? Sheldon didn't apologize when he said my baby looked like Winston Churchill.
Amy: He loves Churchill. Your son should take that as a compliment.
Bernadette: He said it about my daughter.

Bernadette: How many times has he made fun of Howard for being an engineer? Going to MIT? His magic?
Amy: Sheldon doesn't make fun of his magic.
Bernadette: Well, he should. It's stupid.

Bernadette: Anyway, the point is, Sheldon shouldn't dish it out if he can't take it.
Amy: I think the point is that Howard owes him an apology.
Bernadette: Yeah, well, I think the point is if Sheldon has a problem with Howard, Sheldon should take it up with him. Now, if you'll excuse me, the prime minister of England needs her diaper changed.

Leonard: Oh, that's great. He's a Supreme Court justice, and you're the U.S. Constitution.
Anu: Yep. He interprets me. And guess what's underneath this? The Bill of Tights.

Bernadette: Hey, Bert, what are you dressed as?
Bert: I'll give you a hint. My work in seismic refraction measurements and-
Bernadette: Hey, Stuart, what are you dressed as?
Stuart: I'm a butterfly.
Bernadette: Did you steal those from Halley's "let's pretend" box?
Stuart: I'm gonna put them back.

Bert: All right, I'll tell you. I'm Maurice "Doc" Ewing, winner of the 1960 Vetlesen Prize, generally regarded as the Nobel Prize of geology.
Bernadette: Oh, yeah. Now I see it.
Bert: Ask me how I died. Spoiler alert: brain hemorrhage.