while twilight is studying in her library,trixie comes back to pony ville ,but instead of challenging twilight to a duel she gives her a magic mirror and says if she says a certain spell she will look like who she wants in the mirror.

when twilight tries the spell she is sucked into an alternate universe where every won who was a mare was a colt, and every one who was a colt was a mare.

with her appearance changed(along with her cutie mark)can she survive the new residents of ponyville especially the male versions of her friends and herself.