It was presumably based on the original Epic Mickey game. Development never began beyond initial pitches due to Disney's lack of interest.
Very little is known about the film, as the proposal was very quickly turned down by Disney for reasons currently unknown. In a Reddit AMA, Warren Spector mentioned he had sent Disney a few renders and a pitch trailer, but Disney still wasn't interested in the project. Disney still kept the trailer, but no one knows if it still exists.
- Even before the Reddit AMA, Warren had mentioned his interest in a film a few times.
- There are many speculations as to why the film was never made, such as Disney not wanting to make a darker representation of Mickey Mouse into a film (as it would be more "public" than a video game), Disney wanting to focus on other projects, or Disney not having much faith in the franchise. As of now, no one knows the reason.