When the Mayor finds the deed to Monster Isle the monsters move to Townsville causing havoc between monsters and humans.

There's a new Powerpuff Girl in town...or so she would have you think! Her fiendishly foul plot: to trick Santa into turning her into the fourth Powerpuff Girl! (And, in the process, make him believe the Powerpuffs have been very, very naughty!) Now, Bubbles, Blossom, and Buttercup must explode into a Yuletide tornado of bad-girl-thwarting action to put Princess in her place—and keep Christmas from disappearing forever!