Por burlarse del nombre del profesor Pipicaca, Jorge y Beto están a punto de hacer que su nuevo maestro de ciencia enloquecido de rabia se apodere del planeta entero. Pero Capitán Calzoncillos viene al rescate. 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...

George and Harold hypnotize their principal who, believing he is the superhero Captain Underpants, leads them to the lair of the nefarious Dr. Diaper. They must then defeat his evil robot henchmen.