It’s a regular Manhattan Project.

Raj: Have you been selling your sperm again?

Stuart: Here, Sheldon, I pulled the new Hellboy for you. It's mind-blowing.
Sheldon: Excuse me. Spoiler alert.
Stuart: I didn't spoil anything.
Sheldon: You told me it's mind-blowing.So, my mind is going into it pre-blown. And once a mind is pre-blown, it cannot be re-blown.
Stuart: I'm sorry.
Sheldon: Said the Grinch to Christmas.

Howard: Hey, you want to make sure Stuart gets nowhere with Penny without jeopardizing your friendship with either of them?
Leonard: I'm listening.
Howard: Just tell him to do everything you've done with her for the last two years.

Howard: Guys, we have a code red.
Sheldon: Do you mean code red the hospital emergency alert, code red the computer worm, or code red the cherry flavoured soft drink from the makers of Mountain Dew?

Leonard: If you touch her, she’ll break.

Sheldon: For what it's worth, my mother says that when we deceive for personal gain, we make Jesus cry.

Raj: Of course you feel terrible. You completely screwed up your karma, dude.
Sheldon: You don’t really believe in that superstition, do you?
Raj: It’s not superstition. It’s practically Newtonian. For every action, there’s an equal and opposite reaction. Leonard pretends to be a friend and acts like a two-faced bitch, therefore, he is reborn as a banana slug. It’s actually a very elegant system, you know, what goes around comes around.
Howard: Speaking of what goes around comes around…

Raj: If you really want to clean up your karma, go get my freakin’ latte.

Howard: Hold on, you can go to the comic book store when man can once again safely poop in space.

Howard: I got your back, sister.

Sheldon: I don’t see why I have to worry. My career’s not hanging in the balance. That was a joke. It’s funny, because it’s true.