To be clear, only the original versions would have been in public domain for over 40 years. Every time they change something about the character, it creates a new copyright for the new version.

Basically, Steamboat Willie Pete (released in 1928) would have been in the public domain decades ago, but Kingdom Hearts 2 Pete (released in late 2005/early 2006) would have only recently entered the public domain a few years ago.

There are even conspiracy theories that this is why Disney has been so focused on creating awful live action remakes of all of their old works; It resets the copyright timer on the new versions. Disney has historically used copyright as a cudgel to bully smaller content creators, because they took all of the old fairy tales (which were in the public domain) and slapped copyrights on them with their movies.

The conspiracy theory is that the awful live action remakes are simply a way to maintain copyright claims over those original fairy tales. They don’t care if the movies are successful; They just want to prevent anyone in the foreseeable future from ever making a Snow White/Sleeping Beauty/etc film based on the same fairy tales. Because even if a smaller content creator’s work is only based on the original fairy tale, Disney’s army of lawyers can claim that it is based on the Disney version. And the smaller content creators (who can’t afford a long drawn-out legal battle) will be bullied in court and forced to concede.