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?

Leonard: I don't have a problem with Stuart. Besides, he gives us a 20% discount at his comic book store.
Sheldon: Well, I don't sell my friendship that cheaply.
Stuart: I can go 30.
Sheldon: Welcome aboard, old chum.

Sheldon: *Knocks Knock Knock* Empty room (x3). If somebody answers, I'm going to freak out.

Penny: Can I ask you a question?
Sheldon: Given your community-college education, I encourage you to ask me as many as possible.

Sheldon: If you have time to lean you have time to clean.

Sheldon: People of Sheldonopolis, this is your mayor. Follow me. If the children can’t run, leave them behind. Oh, the simulated horror!

Sheldon: Rock - Paper - Scissors - Lizard - Spock

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.

Penny: That is so sad.
Sheldon: No, what's sad is that you don't know Adam West is TV's Batman.

Sheldon: Penny, if I'm going to get Leonard a gift, I'm going to do it right. I refuse to let him experience the same childhood trauma I did.
Penny: I know I'm gonna regret this, but what trauma?
Sheldon: On my 12th birthday, I really wanted a titanium centrifuge so, you know, I could separate radioactive isotopes.
Penny: Of course, yeah.
Sheldon: Instead of a titanium centrifuge, my parents bought me-- Wow, this is hard. They got me a motorized dirt bike.
Penny: No!
Sheldon: What 12-year-old boy wants a motorized dirt bike?
Penny: All of them.

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: My brain is better than everybody's!

Amy: I missed you.
Sheldon: To quote Han Solo, "I know."
Amy: Did you miss me?
Sheldon: I would have preferred to have you there with me.
Amy: Aww.
Sheldon: Or instead of me.

Penny: What's wrong with geology?
Sheldon: Let me put this in a way you'll understand, Penny. You remember you explained to me that the Kardashians aren't real celebrities? Well geology is the Kardashians of science.

Sheldon: I ordered it before you had surgery. It's the urn I was going to put you in.
Penny: Okay, that's morbid. Send it back.
Sheldon: I can't send it back. I had it engraved. "Here lie the ashes of Leonard Hofstadter. He thought he was right, but his roommate knew better."