Sheldon tries to intervene when he discovers a secret about Penny and Leonard on The Big Bang Theory. "The Decoupling Fluctuation" is the second episode of the show's sixth season.
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Raj chills with Leonard and Penny on the sixth season premiere of The Big Bang Theory, titled "The Date Night Variable."
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You're looking at a photo from "The Date Night Variable." It's the first episode of The Big Bang Theory Season 6.
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Kaley Cuoco and Mayim Bialik kick back during this Big Bang Theory scene. It's courtesy of the Season 6 premiere.
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Whoa, what's going on here?!? The gang looks down at Sheldon's odd hairstyle in this scene from The Big Bang Theory.
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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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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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TBBT Quotes

Penny, there's only one cookie with something in the middle that solves life's problems, and that's an Oreo. Or a Nutter Butter, if you're in a pinch.

Sheldon

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.