Thanks for the great ideas everybody! I think I got everybody's figured out for now.
[hider=Nicknames!]
Kameyo - Darlin' and Kame-girl (She gets two cause she's special! :P)
Arty - Hercules
Nick - Handsome
Amaya - Sunshine
April - Sweetheart
Shizuka - Wallflower
Rosanna - Chickadee
Sho - Professor (At least for now. If they ever become friends it might change!)
Jake - Rockstar
Jun - Sugar
Ryva - Songbird
[/hider]

[@Roecoon] I just had Nori climb on top of you like a giant, needy cat. :D