The villains from the popular animated Disney films are gathered at the House of Mouse with plans to take over. Soon, the villains take over the house and kick out Mickey, Donald and Goofy. It's all up to Mickey and his friends to overthrow evil and return the House of Mouse to normal--or as close to normal as it get's.

In the year 3028 A.D., Earth is being attacked by the Drej, which are aliens made of pure energy! The Drej mother-ship destroys Earth with an energy beam just as hundreds of space vehicles manage to escape with the last of mankind aboard! One of the escapees is Sam's young son Cale, who carries with him a ring given to him by his father. Fifteen years later, Cale works on a salvage station, eking out a rough life and hating his father for having disappeared aboard the Titan so long ago. Without a home planet, surviving humans have been reduced to outer space drifters and are constantly bullied and looked down on by other space-faring races. A human captain named Joseph Korso and his pilot Akima seek out Cale and explain that he must help them find the Titan which contains a mechanism that will create a new Earth and therefore unite all of humanity. Meanwhile, the Drej wants to find the Titan so that they can destroy it...

Morgana, sister of Ursula, almost steals the baby Melody from her parents, Ariel and Eric. To protect Melody, she's told never to enter the ocean, but by her 12th birthday, she's been swimming there for years. She discovers the magic locket that was to be her christening gift, which makes her visible to Morgana. Morgana tempts her by offering her fondest wish, to turn her into a mermaid; however, to remain a mermaid, she'll have to steal the magic trident from King Triton (who, unknown to her, is her grandfather). Meanwhile, all the sea creatures are searching for her. Along the way, she joins up with comic relief sidekicks Tip (a penguin) and Dash (a walrus). When she returns with the trident, Morgana's evil nature is revealed, and there is a massive battle of good and evil.