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.

After being sent to jail for the rest of their lives, George and Harold are taken on a trip back in time by Tippy Tinkletrousers back to their Kindergarten days where they must deal with their bully without the help of Captain Underpants.

George, Harold, Captain Underpants, and Sulu the Bionic Hamster battle the three Ridiculous Robo-Boogers in an attempt to turn the Bionic Booger Boy back into Melvin Sneedly.

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.

George, Harold, Captain Underpants, and Sulu the bionic hamster battle the three ridiculous Robo-Boogers in an attempt to turn the Bionic Booger Boy back into Melvin Sneedly.

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, in a story where, by flipping the pages, the reader may view animated illustrations. A snotty situation ensues when Gustavo Lumbreras, an academically-gifted student, turns into the Niño Mocobiónico and must be stopped by Jorge, Berto, and Capitán Calzoncillos.

When Harold and George turn fourth-grade teacher Ms. Ribble into an evil monster called the Wedgie Woman, she wreaks havoc on the world, giving the wedgie of doom to unsuspecting people who stand in her way--including principal-turned-superhero Captain Underpants. When Berto and Jorge turn a fourth-grade teacher into the evil Supermujer Macroelástica, she gives the wedgie of doom to people who stand in her way--including principal-turned-superhero...

George, Harold, Captain Underpants, and Sulu the bionic hamster battle the three ridiculous Robo-Boogers in an attempt to turn the Bionic Booger Boy back into Melvin Sneedly. Jorge, Berto, Capitán Calzoncillos, and Chuli the Bionic Hamster battle the three ridiculous Mocorobots in an attempt to turn the Niño Mocobiónico back into Gustavo Lumbreras.

The adventures of Captain Underpants: When George and Harold hypnotize their principal into thinking that he is the superhero Captain Underpants, he leads them to the lair of the nefarious Dr. Diaper, where they must defeat his evil robot henchmen. Captain Underpants and the perilous plot of Professor Poopypants: When Professor Pippy P. Poopypants comes to Jerome Horwitz Elementary School to teach science, he goes off the deep end because students...