I'm betting Banjo & Kazooie, Ratchet & Clank, and Mario for platform-specific, non-Sega characters. However, making certain Sega characters platform-specific seems like a dick move. In what way could that be helpful to the sales of the game? How many people truly buy multiple copies of the same game on different platforms for their differences? Oh wait, this is a company who has that True Blue Initiative to get people to buy all of the versions of the Sonic 4 episodes. Nevermind.