Sheldon: All right, we're going to be designing an experiment to look for the annihilation spectrum resulting from dark matter collisions in space.
Raj: Ooh, dark matter. We better bring a flashlight, ha, ha.
Sheldon stares at Raj.
Raj: I was making a joke.
Sheldon: I'm the boss. I make the jokes.
Raj: Sorry, go ahead and make your joke.
Sheldon: This is not the time for joking.

Sheldon: Wow, I'm feeling the urge to hug you. And 1, and 2. All right, Gollum, we're good.

Sheldon: The dice giveth and the dice taketh away.

Sheldon: Excuse me, but the problem is not solved. If your head had been accidentally amputated and we transplanted a dog's head in its place, would that be problem solved?
Leonard: If it were your head it would be.

Sheldon: 1234 is not a secure password.

Sheldon: I feel renewed. I'm ready to deal with any changes that come my way. [sees Penny] Your hair is different. You changed your hair. I can't take this. I'm out.

Sheldon: When was the last time you had your menstrual cycle?
Penny: Oh, I'm not answering that Sheldon.
Sheldon: I'm going to say in progress.

Leonard: Do you know how Penny told Raj he should have left her off his list.
Howard: Yeah.
Leonard: Do you think when she and I had that conversation she left people off her list?
Sheldon: I'm sure she did.
Leonard: Why?
Sheldon: Because if she hadn't, she'd still be wading through the list.

Raj: How could you send her away?!
Sheldon: She was late. And she found atomic spectroscopy boring. I wouldn't coitus her with your genitals.

Amy: My old scarf.
Sheldon: You wore it the night we went ice skating, remember?
Amy: You mean the night that I went ice skating and you stood at the rail Googling the symptoms of hypothermia.
Sheldon: We made one heck of a team, huh?

Sheldon: Oh, you don't need to worry about her. She's brilliant and attractive. She can do way better than Leonard.

Sheldon: (To the smoking monkey) You really are an ass.

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.

Sheldon: I don't watch you twenty-four hours a day. I don't know what you do.

Leonard: So now let's bring out theoretical physicist, Dr, Sheldon Cooper.
Sheldon: Hello, female children. Allow me to inspire you with a story about a great female scientist. Polish-born, French-educated Madame Curie. Co-discover of radioactivity. She was a hero of science until her hair fell out, her vomit and stool became filled with blood, and she was poisoned to death by her own discovery. With a little hard work, I see no reason why that can't also happen to any of you. Are we done? Can we go?