Sheldon hires Professor Proton (guest star Bob Newhart) to come to his apartment on The Big Bang Theory. "The Proton Resurgence" is the 22nd episode of the show's sixth season.
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Amy tries to help Sheldon deal when his favorite TV show is cancelled before its proper conclusion on The Big Bang Theory. "The Closure Alternative" is the 21st episode of the show's sixth season.
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Sheldon may experience a roadblock to gaining tenure when he has a history with someone from HR on The Big Bang Theory. "The Tenure Turbulence" is the 20th episode of the show's sixth season.
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Leonard and Penny throw a cocktail party but are their friends adult enough to enjoy it on The Big Bang Theory? "The Closet Reconfiguration" is the 19th episode of the show's sixth 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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TBBT Quotes

Mrs. Cooper: Shelly! I'm so glad you're here!
Sheldon: I saw you having naked sex.

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.