Sheldon: Six times ten to the eighth atoms, Of a radium in a lead jar, Six times ten to the eighth atoms of radium, If the half-life of radium should happen to pass, Three times ten to the eighth atoms, Of a radium in a lead jar.
Penny: Really hope you're almost to zero.
Sheldon: No, see, that's the beauty of half-lives: it's impossible to determine when you'll arrive at zero. It's like "Wheels on the Bus" if the bus had an unknowable number of parts.

Stuart: I'm picking her up in an hour. What am I gonna do?!
Howard: Don't you mean what are you gonna "Oompa Loompa doompety do"?

Penny: Sheldon?
Sheldon: Mm, absolutely not, no. The Nobel committee will be making the calls to inform the winners at any minute, so the only drug I need is the endorphins pumping through my brain in anticipation of our victory.
Amy: Well, technically, anticipation wouldn't be mediated by endorphins as much as dopamine, but, you know, you've been up all night, so I'll give you that one. [Amy looks and sees Sheldon is asleep] Really? The second he stops talking?

Bernadette: Look, it's only a spray tan. It'll fade in a couple days. Why don't you cancel the date and reschedule?
Stuart: Oh, but I was really looking forward to tonight.
Bernadette: You know what? Then go. Tell her what happened. Maybe she'll be flattered.
Howard: And if not, swing by the chocolate factory and see if they're hiring. That wasn't a joke. That was a legitimate suggestion.

Raj: I know that, but I can't do this on my own. I need your help.
Dr. Koothrappali: (sighs) Well, then, I'm going to need your help, too. If I'm going to find a woman to set you up with, you're going to need to stop Instagramming pictures of you and your dog wearing matching sweaters.
Raj: Fine, if that's what it takes to show you that I'm serious. Uh, quick question. Do you mean just Instagram, or all my social?
Dr. Koothrappali: All of them!
Raj: Okay, deal.

Howard: Guys, so what do you think?
Leonard: Well, I don't know, we're pretty happy here.
Penny: Yeah. Plus, if we moved, we'd probably just get a loft downtown.
Leonard: Really? I always figured we'd get a place with a yard.
Penny: Oh, sure, yeah, that makes sense, so you could shoot hoops and mow the lawn?

Sheldon: Uh, don't worry, Leonard, you're still my California best friend.
Leonard: Cool.
Sheldon: So, what do you want to do now? Go to the train store, go to the comic book store?
Tam: Actually, I have to grab my son and head to the airport. I was just about to call a cab.
Sheldon: Don't be silly, you don't have to call a cab. You're my oldest friend. Leonard will take you. Right, Leonard?
Leonard: Sure.

Leonard: Shall we?
Sheldon: Eh, eh, eh, hold on. I haven't seen Tam in 20 years, give me a chance to say good-bye. Bye. [Sheldon walks away]

Leonard: I just don't think you can truly know someone until you've spent a lot of time with them.
Raj: Really? What's Penny's dream vacation?
Leonard: Uh, Malibu beach house.
Penny: That's Barbie's dream vacation. Maybe you should send us that questionnaire.

Sheldon: You just remember the mnemonic: if it's number one, the library's fun, if it's number two, the basement's for you.

Sheldon: Hello, you all remember Tam, my best friend from high school.
Howard: Yeah.
Leonard: Of course.
Raj: How's it going?
Tam: Sheldon's been showing me and my son around. Now we know where all the clean bathrooms are.

Bernadette: Check it out, LeBron James posted a picture of me and him on Instagram.
Penny: I don't see you.
Bernadette: Look right behind him.
Penny: No.
Bernadette: Okay. You see that table just past his left shoulder? Now go back two more tables and over to the right.
Penny: All I see is a yellow smudge.
Bernadette: That's me!

Penny: All right, now what?
Sheldon: Oh, why don't we play a game to pass the time? Here. Uh, I am thinking of a number. Hint: it's a cube of a cube of a prime.
Leonard: There's an infinite number of possibilities.
Sheldon: What, you got somewhere to be?

Raj: Well, I haven't met her yet, but her name is Anu. My father says she comes from a good family. She's in her 30s. She works in hospitality management. So, as long as I can get through six to ten dates without revealing my true self this is happening.

Sheldon: I know just what we're giving them for a wedding gift.