Relena must've been hit on the head last time, otherwise, she would've remembered.

Heero's Birthday
Chapter 1

Heero woke up and thought it was an ordinary day, the sun was up, he could hear Relena making 'breakfast', all seamed to be normal. But, alas this was not an ordinary day, not if Relena had anything to do with it.
"Heero, Heero," Relena shouted "Wake up." "NO!" Was what she heard in reply. To herself quietly she said "Looks like I'll have to drag the birthday boy outta bed."
Birthday boy? Heero thought what did she mean? He had enough time to ponder this while Relena made a pathetic attempt to drag him out of bed.
"Relena." He wouldn't play this game of hear and ponder, "Relena, what did you mean by birthday boy." "Oh my, you don't remember? It's your birthday?!"
The poisoned breakfast wasn't to bad, but what of this birthday. What was she thinking?
"AAAAAAAHHHHHHH!!!!!!!!!!!!! Don't give me wedgie Relena!" Heero yelled
"Happy birthday Heero, Relena invited us over." Hildy waved and said hi.
"What for Duo?" He replied
Quatre walked in and asked "Hey, you guys ready for truth or dare?"
Every one in that room, Relena, Heero, Duo, Hildy, Quatre, Dorothy (she came with Quatre) and the dust bunnies were startled by Wufie arguing with Sally.
"I don't want to play truth or dare with those bakas you onna!"
"Don't call me that!" She sighed "See what I have to put up with?"
Trowa and Catherine shortly fallowed, yet quieter than the previous couple.
Heero was not happy by this invasion, "Relena, what the hell are all these people doing here and what's this about truth or dare!"
Zechs walked in, took one look and said "Looks like a bad party. Let's go." This was answered by Noin grabbing his collar and pulling him in.
"Hey, Heero happy birthday. Sorry about him, I did, however, make him promise not to be so possessive of his sister tonight.
"Goodie, now where is the gun?"
"Relena called up and said she was throwing you a surprise birthday so all of us girls got together and Relena suggested truth or dare. We all thought it was a *cough* semi *cough* good idea." Hildy began to explain this to Heero.
"Fine lets get started already," Everybody nodded "Duo" pause "Truth or dare?"
"Dare"
"Hmmm, what shall I dare? Ok I dare you to strip down to your underwear and sing American Bad Ass!"
*stare* "Consequence?" Duo enquired
"Convince Wufie to sing it." Duo looked over at Wufei. Heero cooked his gun and said "No second consequence."
"I'll do the dare!"
"Good choice Duo." Hildy snickered at Duo. Duo went behind the couch and came out wearing boxers with little chibi Death Scythes on them. The performance was fallowed by swarms of laughter.
*pulls pants on* "I dare....... Sally" Duo paused
"Don't I have a choice?"
"Yep but are you sure?"
"Yes,"
"Positive?"
"Duh!
"Ok, but I warned you." Sally gulps "Tell me the truth about you and Wufei!"
Wufei wipes out katana "INJUSTICE!!!!!"
"That serious. Wow" Duo is amazed
"Hey Noin!"
"Yes Sally, I'll take truth."
"Hm, what's the truth about you and Zechs?"
"Well," sigh "last night we....."
"STOP!!!!!!!" All present yell at Noin to stop, immediately.
"Fine. Trowa, truth or dare?"
"Dare,"
"Ok I dare you to let Duo throw knives at you!"
*gulp* "CONSEQUENCE!!!!!!!!"