Leonard: What would you be if you were attached to another object by an inclined plane, wrapped helically around an axis?
Sheldon: Screwed?
Leonard: There you go.

Leonard: My point is, while you're spending all this time on your own, building computers or practicing your cello, what you're really doing is becoming interesting. When people finally do notice you, they're gonna find someone a lot cooler than they thought. And for those of you that were popular in high school, it's over, sorry. Thank you. Congratulations.

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

Professor Proton: Can I ask you a question?
Leonard: Yeah, sure.
Professor Proton: Why do you put up with Sheldon?
Leonard: Oh, you know because we're friends.
Professor Proton: Why?
Leonard: Wow, you ask really hard questions. Look, I know he can be aggravating, but what you have to remember is he's not doing it on purpose, it's just how he is. But he's also loyal and trustworthy and we have fun together.
Professor Proton: You know you're describing a dog?
Leonard: He did bite me once. But in his defense, I came up behind him while he was eating.
Professor Proton: They hate that.
Leonard: Sheldon is the smartest person I have met. He's a little broken and he needs me. And I guess I need him too.
Professor Proton: Why is that?
Leonard: Boy, you will not let this go, will you?

Sheldon: I remember the song! It's called "Darlin'" by the Beach Boys! Oh, thank goodness! I'm not crazy! I don't have to take a pigeon as my bride!
Leonard: There goes our shot at him living on the roof.

Leonard: You know what, this bottle was meant to celebrate an achievement. Let's make a pact. When one of us gets their first big breakthrough, we'll celebrate by opening this bottle and toasting Professor Abbott.
Howard: I love that.
Raj: Me too.
Leonard: Then, of course, rubbing our success in Sheldon's face.
Howard: Well that's the best part.

Wolowitz: Raj, did you ever tell your sister about the time Sheldon got punched by Bill Gates?
Priya: Oh, God, you're kidding.
Raj: No, Gates gave a speech at the university. Sheldon went up to him afterwards and said, "Maybe if you weren't so distracted by sick children in Africa you could have put a little more thought into Windows Vista."
Leonard: Bam, right in the nose. Made me proud to own a PC.

Leonard: So, for the remainder of my speech, this is for the invisible kids. Maybe you never fit in. Or maybe you were the smallest kid in the school. Or the heaviest. Or the weirdest. Maybe you're graduating and you still haven't even had your first kiss. By the way, nineteen, and Geraldine Coco, wherever you are, thank you. Maybe you don't have any friends, and guess what, that's okay. While all the popular kids are off doing whatever - I don't know what they're doing because I was never there.

Sheldon: *knock knock knock* Leonard? *knock knock knock* Leonard? *knock knock knock* Leonard?
Leonard: What, Sheldon!? What, Sheldon!? What, Sheldon!?
Sheldon: Tell me what you see here.
Leonard: The blunt instrument that will be the focus of my murder trial?

Amy: I just read about an experiment designed to see if you can make two people fall in love in a matter of hours.
Leonard: That doesn't sound right. My research has shown it takes three to five years of shameless begging.
Penny: Honey, neither of us comes off good in that story.

Leonard: Hang on, if you're making all this money, where is it?
Penny: In a safe place.
Leonard: What does that mean, under your bed?
Penny: No, it means a diversified portfolio of stocks and bonds. I'm not overly conservative. I'm young, so my guy said I can afford to take some risks.
Leonard: Wait a minute, you have "a guy"?
Penny: Don't you have a guy?
Leonard: Why would I have a guy?! I don't have any money!

Leonard: Oh, hi, you wanted to see me?
Ms. Davis: Yes. I wanted to talk to you about the e-mail you sent me last night.
Leonard: I sent you an e-mail?
Ms. Davis: You bet you did. "Hello. Shalom and aloha from the grave of Richard Feynman."
Leonard: (groans) Oh, it's coming back to me.
Ms. Davis: "Please accept the following retraction: I know I said physics is dead, but it is the opposite of dead. If anything, it is undead, like a zombie. Speaking of which, if Richard Feynman came back as a zombie, I would totally let him bite me."
Leonard: Any chance that's the end?
Ms. Davis: "I got bit by a squirrel once. I had to get rabies shots. I cried so much, my mother said 'don't be a baby'. In conclusion, physics is great. Squirrels suck, and someday, I'm gonna put my mom in a cheap nursing home. Yours truly, XOXO, Dr. Leonard Hofstadter."
Leonard: I-I-I can explain.
Ms. Davis: "P.S Can you come pick us up? The Uber driver won't open the door because Sheldon is covered in blue vomit."

Sheldon: At my age, do you know how I'm statistically most likely to die?
Leonard: At the hands of your room mate?
Sheldon: An accident.
Leonard: That's how I'm going to make it look.

Leonard: Sometimes your movements are so lifelike I forget you are not a real boy.

Leonard: Penny, you don't want to get into it with Sheldon. The guy's one lab accident away from being a super villain.