Some of the universes could "overlap." For example the Robocop universe and the Star Trek universe could be the same one. We know that San Fransisco had "sanctuary district's
" at one point, so maybe the city of Detroit was taken over by a corporation.
Given the way the real life Detroit is going, would that be so hard to believe?
Harry Potter could possible be in the Trek universe as well. We've seen beings with unusual abilities.
The Terminator universe and the Trek universe histories are too different to be the same.
I don't think that any of these universes make up the same
universe. I'm just wondering if all fictional universes could ultimately be part of one large multiverse. Obviously there's no proof for this, but I just thought it was an intriguing idea.