The Peanut Reaction
Leonard's birthday causes all sorts of madness. Sheldon moonlights as a shop assistant, Howard has an unexpected colonoscopy and a drunken Raj ends up singing 'True Colours'. Who said geeks don't know how to have fun...?
Penny disrupts a game of "trestling" - a game which combines the physical strength of arm wrestling with the mental agility of Tetris - to discuss Leonard's forthcoming birthday. Poor Leonard's never had a birthday party before because his parents focused on celebrating achievements and they didn't consider being expelled from the birth canal to be one of them.
So, after Penny bullies Sheldon to allow a celebratory shindig for Leonard, the gang get organising the surprise party. Penny takes Sheldon to an electronics store to buy Leonard a gift, but ends up besieged by customers thirsty for his technological savvy. Meanwhile, Howard pretends he's suffered an allergic reaction to peanuts so he can get Leonard out of the apartment. Penny's promise that she will tell him which of her friends are easy prompts Howard to actually eat peanuts. Consequently, Howard ends up looking like the elephant man.
By the time Howard's been checked out and had an unnecessary colonoscopy, Leonard's celebrations amount to little more than seeing Raj half-naked singing 'True Colours'. Leonard doesn't get the party, but at least he gets a surprise from Penny that he won't be forgetting in a hurry.