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.
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.
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.

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