This isn't quite confirmed yet, but I trust the person whose blog mentioned reading about this:
"So... how many of you have heard about this strange new game being developed for the Nintendo Wii nicknamed "Epic Mickey" It�s a Disney game in which Mickey Mouse returns to his more old-school-bad-ass roots.
The plot revolves around Oswald the Lucky Rabbit (one of the first characters animated by Walt Disney before Mickey Mouse). Oswald is very unhappy that Mickey has gone on to become a famous star, while he�s been left in the shadows. Using the power of the Phantom Ink Blot, Oswald corrupts and distorts Mickey�s happy Disney World into a twisted menagerie of distorted steam-punk-ish freaks... and it�s up to Mickey to set things right.
That�s already quite strange. But even more intriguing is that players will have a moral compass in the game. You can be as NICE or as MEAN as you want to be, and how you act in the game affects how the rest of the game plays. Apparently the Disney studio is trying to jumpstart Mickey�s career by allowing him to be more mean-spirited and sly like he use to be back in the 1930�s and 40�s.
Even more shocking is that Pixar is working with the game too, and that Warren Specter (sp?) is directing the project. Holy heck... what on earth is this gonna be like? There�s some pretty freakish concept art floating around out there online, so if you fancy a trip down nightmarish childhood fantasies I say take a peek... and certainly keep an eye out for this game... it looks pretty wild!"