Applejack finds a pony at death's door during one of the worst storms of the year. He is bleeding, his wings are broken, and he's unconscious. This new pony has secrets he wants to hide, but as the saying goes, all things must come to light
The mane six wake up as rule 63 versions of themselves. They rapidly begin suffering from gender dysphoria and seek transition back to their former selves, all the while figuring out what sort of monster did this to them.