(not serious) First model created for the Pony mod (which actually exists) for Minecraft, and hey figure the legs would be easy enough to grab the geometry and code from horses or sheep or whatever after they had a few other things worked out?
EDIT:WAlternatively, with the mane and tail being compressible this makes a highly efficient design for getting the most Fluttershy into a given volume for shipment to cuteness and/or kindness deficient areas (and, let's face it, almost anywhere could use more of at least one of those).
What's that? Breathing? Not an issue!

[Source](https://derpibooru.org/images/1256858)
EDIT:
What's that? Breathing? Not an issue!

[Source](https://derpibooru.org/images/1256858)