....and now a Mickey Mouse horror movie is already in works:
https://deadline.com/2024/01/mickey-mouse-horror-movie-trailer-mickeys-mouse-trap-1235693579/Not surprising since last year this happened the year after Winnie the Pooh entered public domain.
Worth noting Disney still has a trademark on Mickey Mouse (which can be extended indefinitely), and still an existing copyright on later versions of the character. This means that for example you could sell a T-shirt with a still from Steamboat Willie on it or Mickey Mouse as he appears in it, but not any later more recognizable forms of Mickey Mouse. Similarly you can make works with a character in it named "Mickey Mouse", but they can't resemble any currently copyrighted/trademarked versions of the character.