Oh, no! It's not enough that George and Harold have invented Captain Underpants, the greatest superhero of all time, and that they've also saved the world FIVE times! Now the boys have to write a one-page report on "good citizenship," and they have been ordered NOT to write a comic about Captain Underpants. So what do they do? They create a brand new superhero: meet Super Diaper Baby -- the most powerful peewee to pack a punch.