"Oh don't worry," Twilight reassured Fluttershy. "It's a simple window spell, what could go wrong?"

A lot, actually.

Applejack, Rarity, Rainbow Dash, Pinkie Pie and Fluttershy watch newly crowned Princess Twilight Sparkle cast a seemingly harmless spell, but it isn't quite like that. It backfires, turning the window into a door, a door which the six friends cannot escape. Their minds, their souls, drift from their bodies into the door. Suddenly, they wake up. One problem. They're in their parallels bodies. They don't know what to do, though their is one thing on their mind.

Escaping.