Trixie accidentally makes a deal with some strange mirror entity that lives in reflections. Out of nowhere, ponies all across Equestria are suddenly swapping bodies.
This causes immediate problems with our favorite horses, with patient zero of the calamity being Twilight Sparkle swapping bodies with Trixie Lulamoon.
The mane 6 (and the new bodies they end up in) must travel to the four corners of Equestria to find a way to fix this mess!