Image: Youtube (Gamehut)
Mickey Mania was a platformer released for the SNES back in 1994, and for the time, it did pretty well. So well that there were plans to make a sequel.
The operative word being were.
Traveller's Tales was the studio responsible for Mickey Mania. If the name rings a bell, it's because the studio is still alive today as TT Games - the company responsible for the LEGO series of platformers and a string of licensed games.
TT were still finding their feet in the early 90's though, at least until Mickey Mania came along. While the game wasn't a critical smash hit, it did well enough commercially to warrant a sequel.
So after its release, the developers knocked up a prototype showing the direction of the game. GameHut has released some footage on YouTube of the prototype. There's no enemies or real obstacles, but you can get a look at the animations, the day/night cycle, and some of the platforming mechanics.
As it mentions early on in the video, Mickey Mania 2 was cancelled after Traveller's Tales were given the opportunity to work on a licensed Toy Story game. That was a side-scrolling platformer as well, and was met with a middling reception (thanks to some truly painful controls) when it released in 1995.