Twilight Sparkle loves Nightmare Night. Planning it, setting it up, pulling it off. Her only wish is that it could last longer. This year, she's decided to make that wish come true. Plunged into darkness, Ponyville must band together on a quest to stop Nightmare Night from becoming Nightmare Forever.

A shapeshifter from another world has landed in Ponyville, intent on bringing chaos and disruption. An ever-curious Pinkie Pie interrupts their plotting, and the shapeshifter's improvisation gets them stuck with the pink pony. They find themselves having to work under Pinkie's nose to try and destroy these ponies' happy lives, but constant exposure to that tsunami of glee is sure to have an effect on anyone.