You're looking at a scene from The Infestation Hypothesis. It's episode two of season five.
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Leonard confronts Penny in this scene from the season five premiere of The Big Bang Theory. She sure finds something funny!
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The gang is all here. And we mean everyone! Check out this scene from the fifth season premiere of The Big Bang Theory.
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This is awkward for everyone. Raj and Penny stand in front of the boys on the fifth season premiere.
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Sheldon takes charge of the paintball team on the season five opener. Is this really a good idea?
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We all know what happened between Penny and Raj on the season four finale. Here they are on the ssason five premiere.
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Amy has so many questions for Penny on the season five premiere. They are all based on sleeping with Raj.
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Bernadette reacts to the news here. Yes, Raj did Penny!
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TBBT Quotes

Sheldon: Are you still mad about the sperm bank?
Leonard: No!
Sheldon: Do you want to hear an interesting thing about stairs?
Leonard: Not really.
Sheldon: If the height of a single step is off by as little as two millimeters most people will trip.
Leonard: I don't care—two millimeters?! That doesn't seem right.
Sheldon: No, it's true! I did a series of experiments when I was twelve; my father broke his clavicle.

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