User blog comment:Slug-Drones/Sonic Generations - Info (does not contain official announcements) *Possible Spoilers*/@comment-24463386-20110913151816/@comment-6671743-20110913153455

Hm, all I know is that the story will consists of missions and one mission out of 5 will have either a co-op of vs with Sonic's friends. E.G. Modern Sonic will co-op with Blaze, but Classic Sonic will VS. Blaze.