Why can anyone now make their own Mickey Mouse cartoon?

Because its copyright ran out. Steamboat Willie, the 1928 cartoon considered Mickey Mouse's official debut, entered the United States public domain on 1 January 2024, more than 95 years after it was released. Once a work is in the public domain, nobody holds exclusive rights to it anymore, so anyone can legally copy, remix or build on it without asking permission, which is exactly what comedian John Oliver announced in April 2023 he would do, making the Steamboat Willie Mickey his show's new mascot as soon as it entered the public domain.

It isn't quite a free-for-all, though. Only the specific 1928 black-and-white version of Mickey, the one without red shorts and gloves, was expected to enter in the public domain; later, more developed versions of the character are still under copyright. And copyright expiring doesn't touch trademark law at all: Disney has used that exact Steamboat Willie image as its own studio logo since 2007, and because trademarks can be renewed forever as long as a company keeps actively using them, Disney may still be able to argue the character is legally protected as a trademark, separate from its copyright status.

The cartoon had been on shaky ground for a while. In the 1990s, a former Disney researcher, Gregory S. Brown, concluded that the film was probably already in the public domain: its 1928 copyright notice had two additional names between Disney and the copyright statement, an error that under the Copyright Act of 1909 would make all copyright claims null. A law student, Lauren Vanpelt, wrote a paper agreeing with him and posted it online in 1999; when a Georgetown University law student later published a paper confirming Brown's claims, Disney threatened to sue for 'slander of title', then chose not to. And in Japan, where the count starts from the death of the last surviving director, Ub Iwerks, in 1971, Mickey most likely entered the public domain in May 2020.