When Penny plans a surprise party for Leonard, she charges Howard with keeping him out of the apartment until it's ready. Howard goes to extreme measures to carry out this task (and to get a chance with Penny's easiest friend). Meanwhile, Sheldon ends up living out a long time fantasy of his.
- Birthday Episode: Penny decides to throw Leonard a Surprise Party because he never got a real birthday party growing up.
- Birthday Party Goes Wrong:
- Discussed. Sheldon mentions what his birthday parties were like when he was a kid and says it was anguish. It's connected to his general hatred of socializing and his status of genius science-oriented kid. Instead of a titanium centrifuge he wanted to separate radioactive isotopes, his parents got him a motorised dirt bike for his 12th birthday which ruined his party.
Sheldon: Sheldon: Year after year, I had to endure wearing conical hats while being forced into the crowded sweaty hell of bouncy castles, not to mention being blindfolded and spun towards a grotesque tailless donkey as the other children mocked my disorientation.
- Leonard mentions he never has a birthday party as a kid and that's why he doesn't celebrate birthdays. Penny, his friendly neighbour (whom he's fallen in love) thinks it's one of the saddest things she's every heard, so she organises a kick-ass surprise party for him. However, Howard is tasked to keep him from the apartment for two hours, but he ends up in hospital (eating peanuts to induce an allergic reaction) so Leonard misses the party.
- Birthday Hater: Sheldon really dislikes celebrating birthdays. It's related to his general aversion to socializing and some mental scars from his childhood when his parents tried to throw him regular kids' b-day parties.
- Blackmail: How Penny gets Sheldon to help plan Leonard's birthday party.
Penny: Okay, here's the deal: either you help me throw Leonard a birthday party, or so help me, God, I will go into your bedroom, and unbag all of your most valuable, mint-condition comic books, and on one of them, you won't know which, I'll draw a tiny little happy face in ink.
Sheldon: You can't do that! If you make a mark in a mint comic book, it's no longer mint.
Penny: Sheldon, do you understand the concept of blackmail?
Sheldon: Well, of course I... Oh! Hey, I have an idea: let's throw Leonard a kick-ass birthday party!
- Body Horror: Howards allergy causes his face to swell up horribly.
- Buffy Speak: The hospital receptionist says "five twin brothers" rather than quintuplets.
- Comically Small Bribe: Howard tries to bribe the receptionist with a $5 bill.
What if I were to introduce you to the man who freed your people? Althea:
Unless my people were freed by Benjamin Franklin and his five twin brothers, you are wasting your time.
- Foreshadowing: Leonard mentioned that whenever he has to buy food for Howard, the restaurants react to Leonard as "AAAH!!! NO PEANUT BOY!!"
- Formerly Fat: Penny bribes Howard into helping her plan a birthday party for Leonard by promising he can pick up her friends, one of whom is a "former fat girl with low self-esteem."
- Never Had a Birthday Party: Leonard. "My family focused on celebrating achievements, and being expelled from a birth canal was not considered one of them."
- Plot Allergy: To stall for time while Penny gets the party ready. Howard fakes an allergic reaction and asks Leonard to drive him to the hospital. When he can't get the receptionist to play along, he has to eat a granola bar with peanuts to trigger a real allergic reaction.