After being invited to Canterlot the mane 6 are taken on a tour of Canterlot Castle by Celestia herself. The point of the tour was to warn them about some of the extremities of magic that can cause serious harm to any and everypony, Pinkie Pie, being the silly pony that she is decided to break off from the group, her absence going unnoticed as the others continued. Eventually Pinkie stumbled in a locked room designed for the end of the tour, the only thing sitting inside was a mysterious mirror…