So I've had some ideas for a potential Epic Mickey sequel for a while, and thought I'd share them. In part, these developed from a desire to see certain abandoned concepts from earlier games finally make their way into the franchise.
So I'm not sure whether I'd want this game to take the place of Epic Mickey 3, or happen after the events of that hypothetical game. In any event, this installment would at long last bring in Ortensia and Minnie as playable characters to join and/or replace Mickey and Oswald. Exactly how their gameplay would work isn't something I've figured out yet. Ortensia being able to petrify parts of herself for combat purposes, a concept considered for Epic Mickey 3, might be a fun one.
In any event, in this story Oswald-if not Mickey as well-would disappear, thus necessitating Minnie being brought to Wasteland to help with the search. Oswald's disappearance would be followed by the emergence of the "Oswald Blot" seen in concept art for the original Epic Mickey. Naturally, it would be assumed that this monstrosity is Oswald himself. The question would become whether he is the victim of some heinous attack, or has caused the transformation himself as evidence of a sinister nature previously concealed.
Ultimately, after working their way through the various minions of this new enemy-possibly including Blackbeard, the Petes (including some additional ones like Garbage and Colonel), the Phantom Blot, and possibly even Mortimer Mouse, together with various Blotlings, Beetleworx, and maybe even Blotworx-our heroes discover that the Oswald Blot is NOT, in fact, Oswald. Rather, the individual who has either transformed themselves into this horrific hybrid, or else created it as a means of securing power as well as destroying Oswald's reputation, is someone else. Someone who, it could be argued, was forgotten even before Oswald, and was only ever seen as an accessory to his fame. Someone who may even hate Ortensia more than Oswald himself:
Fanny Cottontail