The kingdom of Meribella celebrates its 500th anniversary. Famous popstar Keira is giving a series of concerts to commemorate the event; behind the scenes, she is overwhelmed, between being unable to write new songs and dealing with her overeager manager, Seymour Crider. Meanwhile, the fun-loving Princess Tori is pressured by her domineering aunt, Duchess Amelia, and her royal responsibilities. Both girls wish they could trade lives with the other and take it easy. At a royal reception, Keira and Tori meet each other and become fast friends. Using Keira's magic microphone that allows her to change outfits, and Tori's magic hairbrush that allows her to change hairstyles, the girls convincingly disguise themselves as each other, but their necklaces stay the same. Tori shows Keira the royal family's secret magic
gardenia plant which grows diamond-encrusted flowers. The girls take two small diamonds from the plant and attach them to their necklaces. Crider finds out about the diamond gardenia and plans to steal it. Using the magic microphone and hairbrush, the girls plan to switch places for a day and educate one another on their respective lives and routines. While Keira struggles with Tori's royal duties, playing with Tori's little sisters inspires her to write music again. Meanwhile, Tori is having fun rehearsing as Keira, but when freely exploring the kingdom, she discovers how badly the ongoing drought has affected the people. The girls decide to extend the switch for another day and make Keira's final concert a free one so more people can afford to attend. The following night, when the girls are supposed to switch back, Keira is locked in the Princess's bedroom by the Duchess because of a commemorative speech Tori has been procrastinating. Though hesitant at first, Tori is forced to go onstage as Kira and manages to perform. Keira escapes Tori's bedroom through a secret passageway. While the rest of the royal family is at the concert, Crider and his assistant Rupert sneak into the castle to steal the diamond gardenia. They uproot the gardenia, causing the rest of the kingdom's plants to wilt. Tori notices this and rushes back to the castle, where she and Keira change back and intercept Crider. Crider attempts to escape with the plant in a
wingsuit, but the girls stop him by using the microphone and hairbrush to change his outfit; however, in the process, Crider drops the gardenia into the sea. Using the diamonds from their necklaces, the girls plant them in the garden, where they instantly grow into a new diamond gardenia and magically revitalize the kingdom's plant life. The girls rush back to the concert where Keira and Tori perform a spectacular finale together; while sometime later, Tori is shown giving her speech, promising to use her voice to help the kingdom's less fortunate. ==Cast of characters==