@Background Pony #58B7
In this story, a new pony arrives in Ponyville, and nopony thinks anything weird about it at first.
But as time went on, strange things about the new pony begin popping up. Claims of an unusually long tongue, disturbing eyes, octopus-like tentacles extending from back, and other things.
Twilight, being the Princess of Ponyville, investigates and finds that the new pony is not a pony at all. Nor is it a changeling