When Mickey Mouse, along with thousands of other pieces of intellectual property, lapsed into the public domain on January 1, 2024, only the 1928 iteration of the property had its copyright protection removed. So, for Mickey Mouse, it was believed that only the character as he appeared in the three 1928 black and white cartoons was no longer the property of The Walt Disney Company. Any later versions are still protected by Disney's copyright.
In fact, when I drew a comic using Mickey Mouse for publication this year, I was careful to only use the 1928 black-and-white version, and did not depict him as he appeared after 1928 with, for example, eye-outlines around his pupils, or his familiar red-colored shorts. (I did allow him to wear gloves in a few panels, because even if he didn't wear gloves in the narrative of 1928's "Steamboat Willie," he did wear them in the cartoon's title card.
But Alexander Doria, who says he is Head of research at OpSci, points out on BlueSky that a 1928 promotional poster for Mickey Mouse cartoon does feature the character's red shorts, and even yellow gloves, putting those attributes into the public domain and available for anyone to use.
A 2012 Reuters article dates this poster, depicting the mouse in his red shorts, and touting the brand-new character as "The World's Funniest Cartoon Character," at 1928. It sold at that time for $100,000.
