When Professor Pippy P. Poopypants comes to Jerome Horwitz Elementary School to teach science, and he goes off the deep end because students make fun of his name, only Captain Underpants can save the school from the professor's perilous plot.

Crackers and Sulu, the Bionic Hamster, finds themselves in a backwards universe where George and Harold's own evil twins rule the school with the help of the wicked Captain Blunderpants.

Principal Krupp once again turns into the superhero Captain Underpants in order to save the world--and Jerome Horwitz Elementary School--from an army of evil talking toilets.