(Story idea requested by superfun. Takes place before "The Ending of the End".)
In her spare time while preparing to take over the School of Friendship, Starlight Glimmer begins to get into spell experimentation again. And one day she calls Pinkie Pie and Fluttershy over to volunteer with a swapping spell.
When Starlight casts it, Pinkie and Fluttershy inadvertently end up having their personalities completely swapped! Starlight then frantically searches for a way to reverse the effects and return her friends to normal.
Meanwhile, Pinkie Pie and Fluttershy decide that with their swapped personalities it'll be easier if they switch jobs and do each others' work: Pinkie at Sweet Feather Sanctuary and Fluttershy at Sugarcube Corner. Both will soon learn just how difficult the other's work really is, and may just develop a new appreciation for what the work involves.