No need for very much explanation here. This video is the openings (and eyecatches) from the Japanese dub of the 90’s X-Men cartoon. The songs are “Rising” and “Dakishimetai Dare Yori Mo” by Ambience.
The animation here is so much better than in the actual episodes.
How did Cable get so prominent in the first opening? He was only in like three episodes. And the Brood were in less than that.
Comic books obviously provide an easy example of large shared universes; I don’t even need to explain how clearly established it is that Spider-Man, the Fantastic Four, Captain America, Iron Man, the X-Men, and many others exist in the same universe. But let’s see what else Marvel’s characters have interacted with, besides each other, still without crossing universes.
The main Marvel universe contains quite a few characters that Marvel doesn’t have the rights to anymore, though I’m not familiar enough with Marvel’s Godzilla or Conan comics to say whether this counts as a ”probably one way canon” situation or as Marvel just having their own versions of those characters. There’s also Rom the Space Knight (where the comic is the only reason anyone cares about the character) and Shogun Warriors (where Marvels’s version of the robots should be considered unrelated lookalikes to their anime counterparts).
Then there was Archie Meets the Punisher.