I always used Character or Char for short, which is the same number of letters as Toon. The games typically refer to them as your 'character', so I never really understood the whole 'toon' thing other than an intentional knock on the tendency for MMOs to have to compromise on graphics compared to single player games. I can't really say I've ever played one where the world looked far more realistic than the characters though. (I'm not saying they're not out there. Though, even with WoW, as 'cartoony' as it all looked, the world looked just as cartoony as the characters, so there wasn't really any kind of contrast)