Leonard: How about that, Einstein was wrong.
Penny: What?
Leonard: Approaching the speed of light doesn't slow down time, approaching them does.

Sheldon: What self-important preening fraud are they honoring this year?
Leonard: I'm so glad you asked it like that. You!

Leonard: I bet I could throw a rock in this room and come up with three better friends!

Leonard: *Doing Mr. T impression while holding a action figure of Spock with Mr. T's head* I pity the fool who's illogical!

Leonard: Star Wars on Blu-ray.
Penny: Haven't you seen that movie like a thousand times?
Leonard: Not on Blu-ray. Only twice on Blu-ray.
Penny: Oh, Leonard.
Leonard: I know, it's high resolution sadness.

Leonard: Remember the day we first met and you asked me to go to your boyfriend's apartment to get your TV back? And he was 9 feet tall and he took my pants off and you said- What was that? What did you say? Oh, yes, you said you owed me one.
Penny: Oh, come on, that's not fair.
Leonard: I came home with no pants.

Sheldon: Boy, do I have to urinate.
Leonard: If only there were a solution to that.

Sheldon: I couldn't sleep knowing that just outside my bedroom is our living room and just outside our living room is that hallway and immediately adjacent to that hallway is [Penny's messed up apartment]!
Leonard: Do you realize if Penny wakes up there's no reasonable explanation to why we are here?
Sheldon: I just gave you a reasonable explanation.
Leonard: No, no. You gave me an explanation. Its reasonableness will be determined by a jury of your peers.

Leonard: Merry Newtonmas everyone.

Leonard: Oh, I know. This might help. *Gets a ring out of his wallet*
Penny: Where did you get a ring?
Leonard: I've had it for a couple of years. Not important. Penny, will you marry me?
Penny: Oh, my God, yes.
Leonard: This would have been so much more romantic if you didn't have monkey hair on your finger.

Leonard: We're always the good guys. In D&D, we're lawful good. In City of Heroes, we're the heroes. In Grand Theft Auto, we pay the prostitutes promptly and never hit them with a bat.
Sheldon: Those women are prostitutes? You said they were raising money for stem cell research.

Leonard: Where have you been?
Sheldon: Oh, Leonard, if I was prone to sarcasm I'd say I was pulling off a major heist at the museum of laundry baskets.
Leonard: (Counts to 10 and takes a breath) What I meant was, gee Sheldon! You were gone a long time!

Penny: What?
Leonard: He said we should maybe enter you in the killer robot competition.

Howard: Last time I was here, I was a scrawny little nerd.
Leonard: And now you're also an astronaut.

Leonard: There's chapters about potty training, bed wetting and masturbation. Basically, if something came out of me, she wrote about it!