Changelings. They are creatures, yes, but some of them might not LOOK that way. This story is an example.
Not that long ago, there was a young changeling named Ned. When he was very young, he had made a HUGE mistake. He changed into a little Pegasus pony. Queen Chrysalis had thrown poor Ned out of the castle for it and teleported him to Ponyville's orphanage.
After months of waiting, a bright unicorn by the name of Pastel Glitz adopted him. She wasn't that much older than him. She was 22 while he was 20 years old.