In the novel, George Beard and Harold Hutchins turn their principal, Mr. Krupp, into the "greatest superhero of all time", The Amazing Captain Underpants.

It has spawned many sequels and subseries such as Super Diaper Baby, Dog Man, and The Adventures of Ook and Gluk: Kung-Fu Cavemen from the Future.

George Beard and Harold Hutchins are two mischievous fourth-graders who attend Jerome Horwitz Elementary School in Piqua, Ohio.

Back at school, Captain Underpants redresses as Krupp so the boys can reverse the hypnosis, but they have misplaced the ring's manual.

After Krupp leaves with Harold's videotape, George finds the manual and throws it away, failing to notice a warning that immersing a hypnotized person in water will cause them to relapse into their trance at the sound of fingers snapping.

George and Harold return to their usual mischief, but realize they must keep Mr. Krupp from hearing finger snaps, which turns him back into Captain Underpants.