"The bully battle begins! George and Harold are behind bars for a crime they didn't commit, and are soon pulled from prison by a time-traveling tyrant named Tippy Tinkletrousers! Now the boys are going back in time to the carefree days of kindergarten, when the scariest thing they had to face was a sixth-grade bully named Kipper Krupp, the nephew of their clueless school principal. And because George and Harold don't invent Captain Underpants until they're in fourth grade, the clever kindergartners are on their own. Can they beat the bullies with brainpower instead of Wedgie Power?" --back cover.