Howard: What's this? (hand movement)
Sheldon:That's what you did. I assumed, as in a number of languages, that the gesture was part of the phrase.
Howard: Well, it's not.
Sheldon: Why am I supposed to know that? As the teacher, it's your obligation to separate your personal idiosyncrasies from the subject matter.

Sheldon: (Practising speaking Mandarin) Show me your citrus peels.
Penny: Sheldon?
*Sheldon freaks out in Chinese.*
Penny: I'm sorry. Look, do you have a second?
Sheldon: A second what? Pair of underwear?

Howard: Apparently, he posted intimate details of their physical relationship on his blog, which I cannot find anywhere.

Penny: Drop dead, you stupid, self-centered bastard.

Leonard: Sheldon, this date is probably my one chance with Penny. What happens if I blow it?
Sheldon: Well, if we accept your premise, and also accept the highly improbable assumption that Penny is the only woman in the world for you, then we can logically conclude that the result of blowing it would be that you end up a lonely, bitter old man with no progeny. The image of any number of evil lighthouse keepers from Scooby-Doo cartoons comes to mind.

Howard: So you're saying, if in the depths of despair she throws herself at you and demands you take her right there, right now, you'll just walk away?
Leonard: I said I'm her friend, not her gay friend.

Raj: Hey, look, I found an iPod.
Howard: It's smashed beyond repair. What are you gonna do with it?
Raj: What else? Sell it on eBay as slightly used.

Penny: Leonard might be home, can we talk in my apartment?
Sheldon: We're not done?
Penny: No!
Sheldon: Eh, why not? We're already through the looking glass anyway.

Howard: You know, I'm really glad you decided to learn Mandarin.
Sheldon: Why?
Howard: Once you're fluent, you'll have a billion more people to annoy instead of me.

Sheldon: (In Mandarin) Many oxen are in my bed! Many, many oxen!
*Chen flings his hands at Sheldon*
Sheldon: (Mandarin) Oy Vey.

Penny: Hey, jerk face, you forgot your iPod.

Leonard: My parents focused on celebrating achievements and being expelled from a birth canal was not considered one of them.

Penny: You keep him there a little longer, and when you get to the party, I'll point out which of my friends are easy.
Howard: Don't toy with me, woman.
Penny: I got a hot former fat girl with no self-esteem. I got a girl who punishes her father by sleeping around, and an alcoholic who's 2 tequila shots away from letting you wear her like a hat.
Howard: Thy will be done.

Leonard: Here you go, Copenhagen boy, how about a taste of Hans Christian Hand Grenade.

Penny: Hey, guys, some of the other waitresses wanted me to ask you something.
Leonard: It's called trestling.
Howard: It combines the physical strength of arm wrestling with the mental agility of tetris into the ultimate sport.
Penny: Yeah, that's terrific, but what they wanted me to ask you was to cut it the hell out.