Yeah from what I read at an interview article at The Sonic Stadium the only reason Mario and Sonic could be in a game together was only due to a major event like the Olympics, though anyways I wouldn't mind seeing Sonic used as a partner in one of the Paper Mario RPG games, yeah I know that's not that major a spotlight role for Sonic but at least it would have him and Mario working together in something other than Olympic games and with a better story than the Adventure Tours story modes in the handheld versions of these games, plus since Sonic's chatty anyway like the Paper Mario partners, well you'd at least have to admit that's a better idea for a Mario Sonic crossover than a bunch of sports minigames.