Fictional characters, tired of being trapped by extended copyright, escape into the general media.
For many of us, characters in stories can be almost as real as the people we know in life. We enjoy spending time with them. When the story ends we wish for a sequel or ten so we can spend more time with the characters. When we don't like how the story turned out many of us want to create our own version of the story. If the story is old enough, if it's in the public domain, we can do that. If a story is still under copyright we are limited by what we can do with that story and the characters within it.
In recent years, media corporations have fought to extend the copyrights of the works they own in order to continue to profit from those works. Fictional people are keeping other fictional people as indentured servants. The creators of the stories that featured the characters are all dead. They can no longer profit from those stories.
What happens when the fictionals get tired of living in their corporate prisons and decide to romp in the greater imagination?