Wolowitz: Okay, you two have to back off.
Raj: Why should I back off? You back off, dude.
Leonard: Excuse me, this is my apartment, and she's my roommate's sister.
Howard: So what? You've already got Penny.
Leonard: How do I have Penny? In what universe do I have Penny?
Wolowitz: So, I can have Penny?
Leonard: Hell, no!

I'd kill my rabbi with a pork chop to be with your sister

Penny [to Leonard]: Look, you are a great guy, and it is the things you love that make you who you are.
Wolowitz: I guess that makes me large breasts

Sheldon: I propose we add "pants must be worn at all times in the time machine"
Leonard: Seconded.
Wolowitz: I was gonna put down a towel

Leonard: The elevator's been broken for two years.
Sheldon: I've been meaning to ask you. Do you think we should make a call about that?
Wolowitz: Not necessary. I have a Masters in Engineering. I remotely repair satellites in a regular basis. I troubleshoot space shuttle payloads. When the Mars Rover started pulling to the left I performed a front-end alignment from 62 million miles away. [pushes the button...] No, that baby's broken

Leonard: Come on, guys, push!
Howard: If I push any harder I'm gonna give birth to my colon.
Raj: I can't feel my fingers. Hurry up!
Sheldon: It's the same amount of work no matter how fast you go—basic physics.
Raj: Sheldon, if my fingers ever work again, I've got a job for the middle one

Raj: Too bad, I called dibs.
Wolowitz: You can't just call dibs.
Raj: I can, and I did. Look up "dibs" in Wikipedia.
Sheldon: Dibs does not apply in a bidding war

Wolowitz: Don't you think I should answer the engineering question? I am an engineer.
Sheldon: By that logic I should answer all the anthropology questions because I'm a mammal

[Raj whispers in Wolowitz's ear]
Penny: What did he say?
Wolowitz: He compared Sheldon to a disposable feminine cleansing product one might use on a summer's eve.
Penny: Yeah, and the bag it came in

Wolowitz: Oh, more details about the new Star Trek film. There's going to be a scene depicting Spock's birth.
Raj: I'd be more interested in a scene depicting Spock's conception.
Sheldon: Oh, please. For Vulcans, mating—or if you will, pon farr—it's an extremely private matter.
Leonard: Still, I'd like to know the details. His mother was human; his father was Vulcan. They couldn't just conceive.
Wolowitz: Maybe they had to go to a clinic. Can you imagine Spock's dad in a little room with a copy of Pointy Ears and Shapely Rears?

Sheldon: I notice you're using titanium. Did you give any consideration to carbon nanotubes? They're lighter, cheaper, and have twice the tensile strength.
Wolowitz: Sheldon, there is a diploma in my office that says I have a masters in engineering.
Sheldon: And you also have a note from your mother that says, "I love you, bubulah," but neither of those is a cogent argument for titanium over nanotubes

Sheldon: 15 years old. Dennis Kim is 15 years old and he's already correcting my work. Today I went from being Wolfgang Amadeus Mozart to—you know—that other guy.
Wolowitz: Antonio Salieri.
Sheldon: Oh, God, now even you're smarter than me.

TBBT Quotes

Leonard: Hi. I'm Leonard. You are beautiful. You pop, sparkle and buzz electric. I'm going to pick you up at eight, show you a night you will never forget.
Raj: Where are we going?

Penny, there's only one cookie with something in the middle that solves life's problems, and that's an Oreo. Or a Nutter Butter, if you're in a pinch.

Sheldon