“Well, maybe these creatures aren't ponies at all,” thought Snowy Clothes, better known on Earth as Yui Tanaka.
She put aside her phone with her collection of horror stories. “There are tales that grandfather told me — that a distant world can change you into something inhuman, to adapt to the environment when you appear there. And when you return to Earth, you will change back and you don't notice the change. You will also remember things were perfectly normal, that this world was even inhabited by humans. But your memories were changed with your body.
“It would be fun if ponies were actually beings like Nyarlathotep or Shoggoth, but I was changed to see them as equines, just because I like horses.” Yui yawned and looked at the clock. “Oh, time to sleep.
“I always wondered why there are so many worlds, all inhabited by humans,” she thought, drifting into sleep. “Too many humans...”
Yui smiled and suddenly sung in her slumber. “My little Nyarly, my little Nyarly...”