<Li> Kevin Hart as George Beard, a fourth grade student . He is Harold's best friend and writes stories for the comics he and Harold make . </Li> <Li> Thomas Middleditch as Harold Hutchins, a fourth grade student . He is George's best friend and illustrates the comics he and George make . </Li> <Li> Ed Helms as Mr. Benjamin "Benny" Krupp / Captain Underpants, the mean - spirited principal of Jerome Horwitz Elementary School, who is hypnotized into becoming the superhero created by George and Harold . </Li> <Li> Nick Kroll as Professor Pee - Pee Diarrheastein Poopypants, Esq., a scientist angered after being constantly made fun of and not taken seriously for his name, who decides to take over the world to get rid of all laughter . </Li>

Actor who voices captain underpants in 2017 film