"Principal Krupp once again turns into the superhero Captain Underpants in order to save the world, and Jerome Horwitz Elementary School, from the evil talking toilets and the Turbo Toilet 2000"-cProvided by publisher.

En la novena novela, Dav Pilkey lleva a los lectores a los tiempos en que Jorge y Berto estaban en kindergarten, cuando la mayor preocupación de los chicos era un abusón de sexto grado sobrino del director de la escuela. Y como Jorge y Berto no inventaron al Capitán Calzoncillos hasta cuarto grado, los chicos no tienen quien los ayude. No les queda más remedio que usar la cabeza para vencer al abusón.

George and Harold and their doubles, Yesterday George and Yesterday Harold, have been taking turns going to school, but when the doubles fall prey to their gym teacher, Mr. Meaner, and his method of mind control that turns students into attentive, obedient, perfect children, it is up to original George and Harold to strike back. Jorge, Berto y sus dobles, Jorge y Berto de Ayer, la están pasando muy bien. Dos de ellos van a la escuela mientras los...

The monstrous Turbo Toilet 2000 is determined to take revenge on George, Harold, and Captain Underpants.

Only Captain Underpants can stop the three evil space aliens who have invaded Jerome Horwitz Elementary School and turned everyone into lunchroom zombie nerds.

A snotty situation ensues when Melvin Sneedley, an academically-gifted student, turns into the Bionic Booger Boy and must be stopped by George, Harold, and Captain Underpants.