The Adventures of Captain Underpants, by Dav Pilkey, 1997

Life imitates art when George and Harold's confiscated comic books fall into mean ol' Principal Krupp's hands -- and a 3-D Hypno-ring falls into theirs. They've created a monster, who thinks he's a hero, and solves crime with bravado and Wedgie Power. But will it be enough to catch bank robbers, thwart Dr. Diaper and his evil robots, and save George and Harold from a life of servitude and/or a pounding from the football team? There's only one way to find out. Strongly recommended -- if you wear underwear.