The witches of Doom Mountain are tired of the cute, sweet, My Little Ponies that are making their once dreary land bright and happy. Determined to get rid of them, head-witch Hydia and her two daughters concoct the Smose to cover the valley in gloom. The ponies enlist in the help of their human friend, Megan, and the Rainbow of Light to defend themselves. When this doesn't work, they go in search of the Moochick in hopes that he knows a way to fight the horrible purple stuff. In the midst of this chaos, Baby Lickety Split has run away, taking Spike the dragon with her. The pair have a run-in with the Grundles, who agree to help them find their way home.