Wolowitz: Have you thought about putting him in a crate when you're out of the apartment?

Sheldon: I'm clearly too evolved for driving.

Sheldon: Do those sound like castanets to you?
Leonard: The box says 'kitchen'.
Sheldon: So? Do cocaine smugglers write 'cocaine' on the box?

Leonard: I don't think I can go to the North Pole.
Sheldon: OK, Leonard, I know you're concerned about disappointing me, but I want you to take comfort from the knowledge that my expectations of you are very low.

Stephanie: Where did you get the stethoscope and the blood pressure cuff?
Sheldon: My aunt Marion gave them to me for my 12th birthday. She thought if I failed at theoretical physics that I should have a trade to fall back on.

Sheldon: Looking out at your fresh young faces, I remember when I too was deciding my academic future as a lowly graduate student. Of course, I was 14 and had already achieved more than you could ever hope to, despite my 9:00 bedtime. Now, there may be one or two of you in this room who has what it takes to succeed in theoretical physics. It's more likely that you will spend your careers teaching fifth graders how to make paper-mache volcanoes with baking-soda lava.
Leonard: Oh, good God.
Sheldon: In short, anyone who told you that you would someday be able to make any significant contribution to physics played a cruel trick on you. A cruel trick indeed. Any questions? Of course not. I weep for the future of science. Now, if you'll excuse me, the latest issue of Batman is out. Come, Leonard.
Leonard: Laser demonstration's looking pretty good now, huh?

Sheldon: Rock - Paper - Scissors - Lizard - Spock

Sheldon: No one calls me Moon Pie but Meemaw.

Penny: Hey Leonard, what's up with Dr Wackadoodle?

Mrs. Wolowitz:What's going on? Are you boys rough housing?
Howard: We're just talking, Ma!
Mrs. Wolowitz: If you don't settle down right now, I'm not gonna let you have any more sleepovers.
Howard: For God's Sake, Ma, I'm 27 years old. And it's not even a school night.

Leslie: Boy, your heart's racing. I must've really gotten you going.
Wolowitz: Well, it's partly you, partly my transient idiopathic arrhythmia.
Leslie: Sexy.

Sheldon: I believe the appropriate metaphor here involves a river of excrement and a Native American water vessel without any means of propulsion.

Penny: Um, you know it's kinda early. Do you wanna maybe come in for some coffee or something?
Stuart: Oh gee, its a little late for coffee isn't it?
Penny: Aw, you think coffee means coffee. That is so sweet.

Sheldon: I'm surprised you struck out with Penny. Apparently she's a big ol' five.

Ramona: Didn't a great man once say, "Science demands nothing less than the fervent and unconditional dedication of our entire lives."?
Sheldon: He did.
Ramona: And who was that great man?
Sheldon: Me. Sorry, Leonard.
Leonard: Seriously? You're not coming?
Sheldon: You heard her. How can I argue with me?