Howard: Don't feel bad. Some day someone will be throwing out your work, too.
Leonard: That someone was Sheldon and the day was yesterday.

Stephanie: I don't see anything at all, Sheldon.
Sheldon: Well, you're the doctor, but I am constantly hearing this annoying sound.
Leonard: Me too.
Sheldon: Is it a high frequency whistle?
Leonard: No, it's more of a relentless, narcissistic drone.

Penny: What happened?
Leonard: Sheldon's escaped and he's terrorizing the village.

Leonard: What was that?
Penny: Sheldon tried to steal the ring so I punched him.
Leonard: That's my girl!

Sheldon: I've changed. Like the frog who's put in a pot of water that's heated so gradually, he doesn't realize he's boiling to death.
Penny: Or you're the frog who's been kissed by the princess and turned into a prince.
Leonard: Or you're just a tall, annoying frog.

Leonard: I'm the king of foreplay.

Howard: So you're saying, if in the depths of despair she throws herself at you and demands you take her right there, right now, you'll just walk away?
Leonard: I said I'm her friend, not her gay friend.

Leonard: You call that a glow stick? *Pulls out a Lightsaber* That is a glow stick!

Leonard: I'm sorry.
Raj's sister: Why do you say that?
Leonard: When I'm in bed with a girl, that's just my natural response.

Sheldon: How do I make them stop loving me?
Leonard: You could invite them to live with us.

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: 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."

Leonard: Penny. We are made of particles that have existed since the moment the universe began. I like to think those atoms traveled fourteen billion years through time and space to create us, so that we could be together and make each other whole.

Leonard: Can I go back and prevent you from explaining that to me?
Sheldon: Same paradox. If you were to travel back in time and, say, knock me unconscious, you would not then have the conversation that irritated you, motivating you to go back and knock me unconscious.
Leonard: What if I knock you unconscious now?
Sheldon: It won't change the past.
Leonard: But it'd make the present so much nicer.

Leonard: Sheldon, you do this all the time! You fixate on some crazy idea then blow it way out of proportion.
Sheldon: Name one time I've ever done that.
Leonard: How about the time you put GPS trackers in your garbage because you thought North Korean spies were stealing your doodles? The chicken nuggets you thought were human nuggets. The mysterious cloud that was following you around town. Or the time you put my shirt on by accident and thought you were growing again.
Sheldon: I said name one. You need to work on your listening skills.