I don't know your country's law but trademark is just the trademark. Trademark holder can't stop people from using the trademark word. They can stop calling the fake thing as the trademark word because it's not the thing trademark word refer to.
If it is indeed the Mickey Mouse from Steamboat Willie, then it's the Mickey Mouse.
If you lift the images of the strange mouse/person hybrid directly from Steamboat Willy, I would expect that to be legal. But I'm not sure if you could draw your own or not, could Disney have a trademark on the general likeness of the mouse man? I couldn't say. That said, parody/fair use would probably cover your ass for that in practice.
I would expect drawings based solely on thr Steamboat Willy work to be okay. The sequels start new timers on new characters or qualities, they don't extend the copyright on the original work. of course, IANAL.
Maybe explicit branding differentiation, in the style of "Disney's ____" already used to make for distinct branding from other public domain retelling. "Marvel's Superman", that kind of thing.
If it is indeed the Mickey Mouse from Steamboat Willie, then it's the Mickey Mouse.