So, the multiverse has gone haywire. portals are popping up everywhere around the universe, even on normal earth that isn't supposed to have such crazy magic. each portal leads to a different universe, and every time someone steps through a portal they enter a new universe and when they enter that new universe—they automatically are giving an appearance fit for that universe. if an animal (take MLP or Sonic characters for example) enters through certain portals, they could be turned into a human (like for SPN, The Walking Dead, The Last of Us, Marvel, DC, you get the idea) or a different animal (like Beastars, Zootopia, Sonic, so forth) but if a human enters an animal heavy universe they are turned into an animal and you get the jist.