Captain Underpants And The Preposterous Plight Of The Purple Potty People: Color Edition (captain Underpants #8)

By (author) Pilkey Dav; Illustrated by Pilkey Dav
Harold and George's time-traveling Purple Potty lands them in an alternate universe where everything seems delightful, but evil lurks just beneath the surface, and leads to a battle between Captain Underpants and his own evil twin.