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: 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: 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.

Sheldon: Amy, when I look in your eyes and you're looking back in mine, everything feels not quite normal. Because I feel stronger and weaker at the same time. I feel excited and, at the same time, terrified. The truth is, I don't know what I feel, except I know what kind of man I want to be.
Amy: Sheldon, that was beautiful.
Sheldon: I should hope so, that's from the first Spider-Man movie.
Amy: I'll take it.

Sheldon: *knock knock knock* Amy. *knock knock knock* Amy. *knock knock knock* Amy.
[Amy opens the door. Sheldon is on one knee, holding out an engagement ring]
Sheldon: Will you marry me?

Amy: This isn't easy to say, because I love you, but... I need some time to take a step back and reevaluate our situation.
Sheldon: Oh.
Amy: I hope you understand.
Sheldon: Okay.
Amy: Bye, Sheldon.
Sheldon: Well, Gollum, you're an expert on rings. [Sheldon takes out an engagement ring from his desk drawer] What do I do with this one?