After a night dancing, Amy kisses Sheldon. It's their first kiss!
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Sheldon and Amy do a scientific evaluation when she gets turned on by Zach. They determine that she's horny. He wants her to go out with Zach, but instead she tries a hand-holding experiment with Sheldon.
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Don't look for Leonard and Priya to slow down on season five. Not even 7,500 miles can end their relationship!
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Raj and Penny looked as shocked by their actions here as viewers of The Big Bang Theory were. They slept together?!?
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Cheers to a new set up. Raj moves in with Sheldon on the season finale of The Big Bang Theory.
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Sheldon makes a grave mistake in this scene: he drinks from Leonard's glass!
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There is only one Raj.
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Sheldon busts a move on TBBT. Instant fun ensues.
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Howard and Bernadette are seen here during a scene fromThe Big Bang Theory. The photo is courtesy of the episode "The Herb Garden Germination."
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Sheldon and Amy are all about spreading gossip in this photo. It's from the episode "The Herb Garden Germination."
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The men have a mission on the episode "The Zarnecki Incursion." They must find the person who hacked into Sheldon's online game account.
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Can Leonard be friends with Penny while dating Priya? It might be a challenge.
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The Big Bang Theory Season 4 Quotes

Penny: Hey, Sheldon, did you change your Wi-Fi password again?
Sheldon: Yes, it's "Penny, get your own Wi-Fi." No spaces.

Sheldon: Here's an interesting fact about alcohol ... Man is not the only species that ferments fruit in order to become intoxicated. Can you guess what the other is? Hint: sometimes they pack the alcohol in their trunks.
Penny: Monkeys
Sheldon: When does a monkey have a trunk?
Penny: When a suitcase just won't do
Much later - Sheldon: And the answer was elephant.