Bernadette: Sheldon, when was the last time you got any sleep?
Sheldon: I don't know. 2 or 3 days. Not important. I don't need sleep, I need answers. I need to determine where in this swamp of unbalanced formulas squatteth the toad of truth.
Penny: Toad of truth? Is that a physics thing?
Leonard: No, that's a crazy thing.

Sheldon: What is the best number? By the way, there's only one correct answer.
Raj: 5,318,008?
Sheldon: Wrong! The best number is 73. [Short silence] You're probably wondering why.
Leonard & Howard: No no, we're good.
Sheldon: 73, is the 21st prime number, its mirror 37 is the 12th and its mirror 21 is the product of multiplying, hang on to your hats, 7 and 3. Did I lie?
Leonard: We get it! 73 is the Chuck Norris of numbers!
Sheldon: Chuck Norris wishes! In binary, 73 is a palindrome, 1001001, which backwards is 1001001, exactly the same. All Chuck Norris gets you backwards is Sirron Kcuhc!
Raj: Just for the record, when you enter 5,318,008 in a calculator, upside down it spells boobies.

Leonard: She's not going to steal our idea.
Penny: What idea?
Leonard: We're gonna write an application...
Sheldon: [sings] The prairie sky is wide and high, deep in the heart...
Penny: Okay, stop, stop!
Sheldon: [meekly] ...of Texas.

Sheldon: Who's ready to laugh? [Leonard groans] Okay. So Feynman, Einstein and Schrodinger walk into a bar. Feynman says, "It appears we're inside a joke." Einstein replies, "But only to an observer who saw us walk in simultaneously." To which Schrodinger says, "If someone's looking in the window, I'm leaving."
Leonard: [chuckles] That's actually funny.
Raj: You should send that to Jimmy Fallon.

Penny: So, how you been?
Sheldon: Well, my existence is a continuum, so I've been what I am at each point in the implied time period.
Penny: You're just coitusing with me, aren't you?
Sheldon: Bazinga!

Sheldon: I should've brought an umbrella.
Leonard: What for? It's not going to rain.
Sheldon: I know that, but with skin as fair as mine, moon burn is a real possibility.
Howard: That's a bazinga, right?
Sheldon: One of my best, don't you think?

Sheldon: [through virtual presence device] This is a photograph of the 1911 Solvay Conference on the theory of radiation and quanta. Using Photoshop, I've introduced a few anachronisms. See if you can spot all 24. I'll give you the first one. Madame Curie should not be wearing a digital watch. And go.
Leonard: That’s it. Bye-bye. [turns off screen]
Sheldon: [screen turns on] Bazinga.
Leonard: Whoa! [car swerves]
Sheldon: I have an override switch.
Leonard: I almost died!
Sheldon: And I'm safe and sound in bed. Who's crazy now?
Leonard: I'm still going to go with you.

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: 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: Does this mean you're not going to sing Soft Kitty?
Mary: No, I will always sing you Soft Kitty. [sings] Soft kitty, warm kitty, little ball of fur…
Leonard: [opens door] Mrs. Cooper, were we supposed to take that pie out of the oven?
Sheldon: Get out!
Mary: Well, that was rude.
Sheldon: Well, I know, but he means well. Sing.
Mary: [sings] Happy kitty, sleepy kitty…
Sheldon: What are you trying to pull, Mom? From the top.
Mary: [to God] This is what I'm talking about. [sings] Soft kitty, warm kitty, little ball of fur…

Sheldon: [through virtual presence device] Sing me Soft Kitty.
Penny: Really, you want me to sing Soft Kitty to a computer monitor?
Sheldon: Would you rather come over and sing it to me in person?
Penny: [sings] Soft kitty, warm kitty, little ball of fur.
Sheldon: Closer to the microphone.
Penny: Happy kitty, sleepy…
Sheldon: No. You have to start over.
Penny: [sings] Soft kitty, warm kitty, little ball of fur. Happy kitty, sleepy kitty, purr, purr, purr.

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.

Sheldon: Can you sing Soft Kitty?
Penny: What?
Sheldon: My mom used to sing it to me when I was sick.
Penny: I'm sorry, honey, I don't know it.
Sheldon: I'll teach you. [sings] "Soft kitty, warm kitty, little ball of fur, happy kitty, sleepy kitty, purr purr purr." Now you.
Penny: [sighs] [sings] Soft kitty, warm kitty…
Sheldon: Little ball of fur. Keep rubbing.
Penny: Little ball of fur.

Sheldon: Just a few more signatures, and we'll be finished. Initial here to acknowledge that you've returned your key. Okay. As my future neighbor, I'd like you to have a key. Initial here to acknowledge you received it.

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.