Sheldon makes Leonard pays for a past mistake on The Big Bang Theory. "The Itchy Brain Simulation" is the eighth episode of the show's seventh season.
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Sheldon feels like a fraud with his latest scientific breakthrough on The Big Bang Theory. "The Romance Resonance" is the sixth episode of the show's seventh season.
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Sheldon, Howard, and Leonard give a presentation about careers in science to a group of girls in junior high on The Big Bang Theory. "The Contractual Obligation Implementation" is the 18th episode of the shows sixth season.
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Koothrapali refuses to leave his apartment after a bad date on The Big Bang Theory. "The Monster Isolation" is the 17th episode of the show's sixth season.
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Who would guess that Penny and Leonard's Valentine's day wouldn't go as planned on The Big Bang Theory? "The Tangilble Affection of Proof" is the 16th episode of the show's sixth season.
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Leonard and Sheldon's fight spills over into everyone else's lives on The Big Bang Theory. "The Spoiler Alert Segmentation" is the 15th episode of the show's sixth season.
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Game night turns into a messy battle of the sexes on The Big Bang Theory. "Re-Entry Minimization" is the fourth episode of the show's sixth season.
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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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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.