For some reason, Raj, Leonard and Wolowitz join Sheldon in helping Penny manufacture 1000 Penny Blossoms. The things a nerd will do for a pretty girl.
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Sheldon and Penny sit down and sing a sea shanty as they make Penny Blossoms (Penny's hair berets). You have to hear / see it to belive it.
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Leonard plays laser obstacle chess with the guys. What is laser obstacle chess? Glad you asked. You must avoid the lasers in order to make your next move.
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The Big Bang Theory Season 2 Episode 18 Quotes

Sheldon: I'm a physicist. I have a working knowledge of the entire universe and everything it contains
Penny: Who's Radiohead?
Sheldon [after twitching for a minute]: I have a working knowledge of the important things

Howard: you know what would bea great idea? We get some girls over here and we play laser obstacle strip chess
Leonard: Believe me howard, any girl who would want to play that, you don't want to see naked
Howard: You underestimate me