Princess Cadance invites Twilight and her friends, as well as Princess Luna to The Crystal Empire for a week long vacation and coming along with them, with Cadance's permission, are Fleur de Lis and Fancypants. However, the day after their arrival in the empire, opposite gendered versions of all of the current residents and visitors to The Crystal Empire suddenly appear. Now, the two universes' residents must work together to figure out who came to whose dimension, and get them home.

Meanwhile, at least one pony has decided that this would a good opportunity to play matchmaker for two dimensions while all this is sorted out.