Leo set up everybody's Facebook accounts. But that meant he chose the username.

Percy: AquaMan

Annabeth: ScaryAthenaDemigodnessChildWhoWillProbablyKillMe

Hazel: The-one-with-the-farting-ferret

Frank: Candainbabyfaceman

Piper: Pipesthebeautyqueen

Jason: Sparky-McBrick-Face

Nico- Shadowdeathdude