My entry into FanOfMostEverything's Villain Exchange Program contest. The limitation is Write a story with a pony villain in the human world, or vice versa.
So at the castle of the Two Sister's Nightmare Moon attempts to defeat Celestia and take over Equestria, a classic story. However, when Celestia turns the battle in her favour, instead of locking Luna in the moon, for some reason she ends up in a world populated by humans.
This is set a few months after that, part way through her travels, and instead of being the entire story, we simply see a small slice of the adventure.
After all, what kind of person would I be if you got the entire story? XD