Harold and George's time-traveling Purple Potty lands them in an alternate universe where everything seems delightful, but evil lurks just beneath the surface, and leads to a battle between Captain Underpants and his own evil twin.

In the house of Helios, god of the sun and mightiest of the Titans, a daughter is born. But Circe is a strange child -- not powerful, like her father, nor viciously alluring like her mother. Turning to the world of mortals for companionship, she discovers that she does possess power -- the power of witchcraft, which can transform rivals into monsters and menace the gods themselves. Threatened, Zeus banishes her to a deserted island, where she hones...