The Big Bang Theory Season 4 Episode 11

Zack: I saw this great thing on the Discovery Channel. Turns out, if you kill a starfish, it'll just come back to life.

Zack: The costume came with a black wig. Where is it, babe?
Penny: I'm not wearing it. It looks stupid.
Zack: Come on, we're trying to win a contest here.
Penny: Forget it! I'm not wearing the wig.
Zack: Penny, there's no "I" in "Justice League".

Sheldon: Milk-Duds, with their self-deprecating name and remarkably mild flavor, are the most apologetic of the boxed candies.

Leonard: Do you think Penny's right? Were we bullying Zack?
Howard: No, I know bullying. He left here un-swirlied, and his ass-crack was underpants-free.

(after Sheldon has just cheated by throwing in a self-made card)
Leonard: Do you understand why people don't want to play with you?
Sheldon: No, but it's a question I've been pondering since pre-school.

(playing a card game)
Raj: (throws card) Water Demon.
Howard: (throws card) Ice dragon.
Leonard: (throws card) Lesser Warlord of Kahaa (smugly reaches to collect the 'winnings').
Sheldon: Not so fast (throws card). Infinite Sheldon.
Leonard: Infinite Sheldon?
Sheldon: Yes. Infinite Sheldon beats ALL other cards. And does not violate the rule against homemade cards because I made it at work.

Leonard: Zack, this is Stuart. He owns the store.
Zack: Wow, lucky you!
Stuart: Yeah, I work 70 hours a week and average $1.65 an hour.
Zack: Sweet!
Stuart: Is that sarcasm?
Howard: No, it's an indictment of the American education system.

Zack: You were making fun of me.
Leonard: Come on, that's what we do! We give each other a hard time. (turns to demonstrate) Hey Sheldon, you look like a praying mantis.
Sheldon: That's very hurtful.
Leonard: See?

(at comic book store)
Zack: Wow, this place is awesome. Where do they keep the Archies?
Sheldon: In the bedrooms of ten-year-old girls, where they belong.

(planning to give Zack the role of Superman)
Howard: He's the only person we know with actual muscles.
Leonard: You can't replace me with Zack!
Howard: Why not? Penny did it. She seems happier, why wouldn't we?

Penny: (hearing knocking) Go away, Sheldon!
Leonard: (through door) It's Leonard.
Penny: Oh. (beat) Go away, Leonard.

Zack: I haven't been to a comic book store in literally a million years.
Sheldon: Literally? Literally a million years?

Sheldon: Wonder Woman was an Amazon. And Amazons tend to be very beefy gals
Penny: Goodbye, Sheldon! (slams door in his face)
Sheldon: (through door) But they're not blonde, so put on your wig!

Sheldon: Amy Farrah Fowler doesn't believe in wearing costumes. She isn't the free spirit I am.