Penny: So, you know, isn't there maybe some way you and Sheldon could compromise on this whole presentation thing?
Leonard: No. Scientists do not compromise. Our minds are trained to synthesize facts and come to inarguable conclusions. Not to mention Sheldon is bat-crap crazy

Leonard: Are there any other honors that I've gotten that I don't know about? Did UPS drop off a Nobel Prize with my name on it?
Sheldon: Leonard, please don't take this the wrong way, but the day you win a Nobel Prize is the day I begin my research on the drag co-efficient of tassels on flying carpets

Leonard [watching their fight on YouTube]: Oh, geez, does this suit really look that bad?
Sheldon: Forget your suit. Look at my arms flailing. I'm like a flamingo on Ritalin

Leonard: Sheldon, why is this letter in the trash?
Sheldon: Well, there's always the possibility that a trash can spontaneously formed around the letter, but Occam's Razor would suggest that someone threw it out

Leonard: You are not Isaac Newton.
Sheldon: No, no, that's true. Gravity would have been apparent to me without the apple

Leonard [referring to Sheldon singing]: What got into him?
Penny: Oh, just a couple virgin Cuba Libres that turned out to be kinda slutty

Leonard: Look at the bright side. [Lalita] might turn out to be a nice, beautiful girl.
Raj: Great, then we'll get married, I won't be able to talk to her, and we'll spend the rest of our lives in total silence.
Wolowitz: Worked for my parents

Penny [to Raj about Lalita]: No one can make you get married. Why don't you just meet this girl and see what happens?
Raj: Haven't you been listening to me? I cannot talk to women!
Leonard: Um, Raj?
Wolowitz: No, no, let's see how long it takes him

Sheldon: When I was a little boy and got sick, which was most of the time, my mother would read [The Monkey and the Princess] to me. It's about an Indian princess who befriends a monkey who was mocked by all the other monkeys because he was different. For some reason I related to it quite strongly.
Penny: I know the reason.
Leonard: We all know the reason

Penny: I need some guinea pigs.
Sheldon: Okay, there's a lab animal supply company in Reseda you can try. But if your research is going to have human applications, may I suggest white mice? Their brain chemistry is far closer to ours.
Penny: I swear to God, Sheldon, one day I'm going to get the hang of talking to you.
Leonard: His mom's been saying that for years

Leonard: Do you really need the Honorary Justice League of America Membership card?
Sheldon: It's been in every wallet I owned since I was five.
Leonard: Why?
Sheldon: It says keep this on your person at all times. It's right here under Batman's signature.

Penny: Hey, if you guys need a fourth, I'll play.
Leonard: Great idea!
Sheldon: Uh, no. The wheel was a great idea. Relativity was a great idea. This is a notion, and a rather sucky one at that.
Penny: Why?!
Sheldon: Why? Oho, Penny, Penny, Penny.
Penny: Oho, what, what, what? [picks up controller]
Sheldon: This is a complex battle simulation with a steep learning curve. There are a myriad of weapons, vehicles, and strategies to master, and not to mention an extremely intricate back story.
Penny: Oh, cool! Whose head did I just blow off?
Sheldon: Mine.

TBBT Quotes

You can't ruin a friendship with sex that's like trying to ruin ice cream with chocolate sprinkles.

Raj

Sheldon: Even the dung beetle chooses to plot its course by using the Milky Way.
Raj: Is that true?
Sheldon: Everything I say is true. Now, of course, the dung beetle also enjoys eating fece, living in feces and making little balls out of feces. So, pick and choose which aspects of its lifestyle you want to embrace.