Leonard: Refresh my memory. Why didn't I just put you in the trunk?
Sheldon: Because I called shotgun, remember?

Sheldon: Pay no attention to that man in the bed.

Sheldon: (Trying to keep Leonard from reaching his room) Wait. Come back. Halt. Authorized personnel only.

Penny: The Flash shirt is what? Because you're gonna run really fast?
Sheldon: No, the Flash shirt is because it's Friday. But it's nice when things work out.

Howard: (Repeating what Raj says) You're right, Penny jogs. Maybe you guys can run together.
Sheldon: That's an excellent idea. Yeah, if we chat, it will create the illusion of time going faster.
Penny: No, it won't.

Penny: That's amazing.
Sheldon: I wouldn't say amazing. At best it's a modest leap forward from the basic technology that gave us Country Bear Jamboree.
Howard: Hey, Sheldon? Ahem.
Sheldon: Yes?
*Howard commands the robot arm to perform a hand gesture*
Sheldon: Peace?
Howard: No, not peace. Hang on.

Sheldon: What's the sixth noble gas?
Leonard: Uh, radon?
Sheldon: Are you asking me or telling me?
Leonard: Telling you?
(Sheldon gives Leonard a stern look)
Leonard: Telling you.

Sheldon: Explain to me why Wil Wheaton and his lackeys get in and we don't.
Movie Attendant: Because I'm the petty functionary with the clipboard, bitch.

Sheldon: I present to you the Relationship Agreement. A binding covenant that in its 31 pages enumerates, illuminates and codifies the responsibilities of Sheldon Lee Cooper - hereinafter referred to as the "Boyfriend" - and Amy Farrah Fowler - hereinafter referred to as the "Girlfriend.
Amy: That's so romantic!
Sheldon: Mutual indemnification always is.

Amy: How did you get into my apartment?
Sheldon: Wow. Is that the kind of nagging I can expect now that you're my girlfriend?

Sheldon: (knock, knock, knock) Penny!
(knock, knock, knock) Amy!
(knock, knock, knock) Bernadette!

Leonard: Cause of death for Uncle Carl was KBB? What's KBB?
Sheldon: Killed by badger.
Leonard: How's that?
Sheldon: It was Thanksgiving. Uncle Carl said, "I think there's a badger living in our chimney. Hand me that flashlight." Those were the last words he ever spoke to us.

Sheldon: Impressive, but we must be cautious.
Howard: Why?
Sheldon: Today, it's a Chinese-food-retrieval robot. Tomorrow, it travels back in time and kills Sarah Connor.

Leonard: Do you think I'm overdressed?
Sheldon: It depends on the activity. For a prostate exam? Yes. If you're playing Vegas, I'd add sequins.

Penny: Really? On top of everything, you're afraid of birds?
Sheldon: Its called ornithophobia and someday it will be recognized as a true disability, and the landlord will be required by law to put a giant net over the building. Which is unfortunate because I have a fear of nets.