My Little Pony Transformers Prime: Castle Mane-ia is a new movie.
Twilight and Optimus go to Celestia and Luna's old castle to research the chest from the Tree of Harmony, finding a diary kept by the sisters that explains the workings of the castle. Meanwhile, Applejack, Bulkhead, Arcee and Rainbow Dash challenge each other to stay the night in the castle, which they believe is haunted by the Cybertronian of Shadows, while Rarity and Bumblebee take Fluttershy and Ratchet along to the castle to look for old tapestries to repair. The eight inadvertently get into several hijinks of traps and devices triggered by themselves, as well as an unknown pony playing on the castle's organ, thought to be the Cybertronian of Shadows. Twilight and Optimus find the eight in a state of panic and calms them down, and together they find the organ player to be Pinkie Pie and Smokescreen, who had followed their friends to the castle, thinking there would be a party.