The greatest trick the Great and Powerful Trixie ever performed was convincing all of ponykind that she was a mere unicorn. Years later, Princess Celestia and Trixie have a discussion by Twilight Sparkle's grave.
Following the final Magic Duel, Ponyville holds Trixie in custody until she can be attended to by one of the Princesses. However, when Celestia arrives with Prince Blueblood in tow, a shocking truth awaits the residents of Ponyville.