Friendship Sentai Ponyranger: The Movie: Princess of Light, Princess of Darkness
After many battles and struggle, the Ponyrangers were able to track down Nightmare Moon, and faced her for one final battle in the ancient castle she and Celestia had once called home. Together, they were able to use the power of the Elements of Harmony to defeat Nightmare Moon, and with Celestia's help, they restored Princess Luna to her true form. Afterwards, Celestia told them that though the fight with Nightmare Moon was over, the world of Equestria still needed protection. And so, after several peaceful months....
Twilight Sparkle and her friends receive shocking news: Twilight's older brother, Shining Armor, is to be wed to Cadance, the Princess of the remote Cadenza Island. Twilight, and all her friends, have been invited to attend. Having not seen Shining since she was a child, Twilight is both eager to reconnect and afraid that there may not be room in Shining's life left for her to do so.
But there is a grave secret on Cadenza Island...a reason that there is a carefully-maintained Force Field around it that has been maintained for many thousands of years, and which Shining Armor now maintains. For beneath the ground of the island, there sleeps an army of creatures called Changelings, shape-shifters who feed on the life-force of living creatures, and which once tried to take over the entire world until they were imprisoned in eternal hibernation.
Twilight soon finds reason to fear that Cadance is maniupulating Shining Armor, and doing so in the name of awakening the Changelings and unleashing them upon the world. Now, she and the rest of the Ponyrangers must work together to stop this plan before it's too late. But can they save the island, the world, and Shining Armor?