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.

Jorge and Berto have really done it this time-- they've created a monster! She's faster, smarter, and more evil than anything the world has seen before--she's Supermujer Macroelástica! With the help of her horrible robots and her horrendous hairdo, Wedgie Woman is on a mission to take over the world, and she'll give a whopping wedgie to anyone who stands in her way--including Capitán Calzoncillos. Will Wedgie Woman's wicked ways spell the end for...

When Professor Pippy P. Poopypants comes to Jerome Horwitz Elementary School to teach science, and he goes off the deep end because students make fun of his name, only Captain Underpants can save the school from the professor's perilous plot.