Sheldon is a nice guy. But he can also be a very demanding friend toward Leonard, as evidenced here.
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They're back together! All seems right in the world when Penny is dating Leonard, don't you agree?
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It's a romantic evening for two on the 100th episode of The Big Bang Theory. We're very jealous of Leonard.
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The men of The Big Bang Theory do their thing in this shot from the sitcom. It's courtesy of the episode "The Shiny Trinket Maneuver."
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Leonard needs some advice in this Big Bang Theory scene. He has come face to face with his high school bully.
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Can Leonard and Penny hang out alone? That's their goal in this Big Bang Theory scene.
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Laurie Metcalf is seen here as Sheldon's mom. She is rather popular within the group.
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Wil Wheaton is back! And he's hosting a party at his house here.
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TBBT Quotes

Penny: Here's a question-- as an alien pretending to be human, are you planning to engage in any post-prom mating rituals with Amy?
Sheldon: There are post-prom mating rituals?
Penny: Not always. Unless your date drives a van with an air mattress, then always.
Sheldon: Well, if it's part of the prom experience, then I'm open to it.
Penny: You're kidding.
Sheldon: I may be an alien, but I have urges.If Amy wants to copulate by firing her eggs into space, well, then, I will happily catch them with the reproductive sac on my upper flermin. I'm not the best at reading facial cues, but I can see that you're a little turned on.

Raj: Well, to paraphrase Shakespeare: It's better to have loved and lost than to stay home every night and download increasingly shameful pornography.
Penny: Oh... you poor baby.
Raj: What's wrong with me, Penny?
Penny: Nothing, nothing. You know, if we weren't friends - and you hadn't brought up that creepy pornography story - I'd be on you like the speed of light squared on matter to make energy.
Raj: Hey, you totally got that right. E = MC squared.
Penny: I listen. I have no idea what it means, but I listen.