Penny: Uh, hey, guys, guys, you will really appreciate this, I read the best science joke on the Internet. Alicia, you won't get it, but it's right up their alley. Anyway, so, this physicist goes into an ice cream parlor every week and orders an ice cream sundae for himself, and then offers one to the empty stool sitting next to him. This goes on for a while until the owner finally asks him what he's doing. The man says, "Well, I'm a physicist, and quantum mechanics teaches us that it is possible for the matter above this stool to spontaneously turn into a beautiful woman who might accept my offer and fall in love with me." The owner then says, "Well, lots of single, beautiful women come in here every day, why don't you buy an ice cream for one of them, and they might fall in love with you?" And the physicist says, "Yeah, but what are the odds of that happening?"
Leonard: It's a little insulting, don't you think?
Penny: How would I know? I'm not even sure I get it.

Penny: Here you go, [to Leonard] quesadilla, [to Howard] salad, [to Raj] here's your pizza. And thanks to Sheldon's heated discussion with my manager, one barbecue bacon cheeseburger, barbecue sauce, bacon, and cheese on the side.
Sheldon: Thank you!
Penny: Go ahead. Eat it. I dare you!

Leonard: [to a "smiling" Sheldon] We're here to see Koothrappali, not kill Batman.

Sheldon: Did you bring the dehydrated low-sodium soy sauce?
Leonard: Check.
Sheldon: Freeze-dried spicy mustard?
Leonard: Check.
Sheldon: Flash-frozen brown rice, not white?
Leonard: Uh, oh, sorry.
Sheldon: Not to worry. I hid it. Bazinga!

Sheldon: Oh, boy.
Leonard: What?
Sheldon: I can't comment without violating our agreement that I don't criticize your work.
Leonard: Then what was "Oh, boy"?
Sheldon: Great restraint on my part.
Leonard: There's nothing wrong with the science here.
Sheldon: Perhaps you mean a different thing than I do when you say science.
Leonard: [makes a change] Okay, how's that?
Sheldon: You actually had it right in the first place. Once again, you've fallen for one of my classic pranks. Bazinga!

Sheldon: Sing Soft Kitty.
Penny: That's only for when you're sick.
Sheldon: Homesick is a type of being sick.
Penny: Come on. Do I really have to?
Sheldon: I suppose we can stay up and talk.
Penny: [sings] Soft kitty, warm kitty, little ball of fur. Happy kitty, um…
Sheldon: Sleepy kitty.
Penny: Sleepy ki…
Sheldon: No. Start over.
Penny: [sings] Soft kitty, warm kitty, little ball of fur. Happy kitty, sleepy kitty, purr, purr, purr.

Penny: Leonard, I don’t know what to tell you. It was just a hug.
Leonard: Glad we cleared that up.
Penny: Yeah.
Leonard: I guess I'll see you.
Penny: Okay, have a safe trip.
Leonard: Thank you. Bye.
Penny: Okay, bye. [closes door] It means I wish you weren't going.

Sheldon: When I try to deceive I have more nervous ticks than a lime disease research facility. It's a joke. It relies on a homonymic relationship between the tick the blood sucking arachnid, and tick the involuntary muscular contraction. I made it up myself.

Wolowitz: As delicious as the appetizer may be, sooner or later we will have to succumb and eat the entree while its still ... hot.

Sheldon: Oh, Penny. I know you think you're being generous, but the foundation of gift-giving is reciprocity. You haven't given me a gift, you've given me an obligation.
Howard: Don't feel bad, Penny. It's a classic rookie mistake. My first Hanukkah with Sheldon, he yelled at me for eight nights.

Sheldon: The horror!
Penny: Sheldon, I'm sure it's going to be fine.
Sheldon: No, it's not going to be fine. Change is never fine. They say it is, but it's not.

Penny: Oh, alright. I will give you my bed on one condition. That you promise to zip your hole for the next eight hours.
Sheldon: May I say one last thing.
Penny: Only if it doesn't rhyme.
Sheldon: Alright. Goodnight.

Sheldon: So, how was your day?
Penny: Are you trying to make small talk? Oh, sweetie, you really don't have to.
Sheldon: No, it's the accepted convention. How was your day?
Penny: Well, uh, they shifted my schedule around at the restaurant so my hours are going to be a little different...
Sheldon: I'm sorry, that's not going to interest me at all, just eat.

Mikayla: You want the girlfriend experience.
Leonard: Yes, yeah, exactly, the girlfriend experience.
Raj: Uh, actually, if it's not too much to ask, could we have the Jewish girlfriend experience.

Sheldon: I was Spock. Are you and Leonard friends with benefits?
Penny: What?
Sheldon: Are you and Leonard friends with benefits?
Penny: Where did that even come from, did he say we were?
Sheldon: No, Leonard said nothing, but who knows what goes on over here when he pretends your mail was mis-delivered.
Penny: No, just mail, no benefits.