<Ul> <Li> Jim Carrey as Horton the Elephant , an outgoing , eccentic , big - hearted , loving , sweet , and thoughtful elephant and teacher in the Jungle of Nool . Horton has no tusks , lives by himself and possesses acute hearing abilities . </Li> <Li> Steve Carell as Mayor Ned McDodd , the mayor of Whoville . He has 96 daughters , 1 son named JoJo and a wife named Sally . </Li> <Li> Carol Burnett as Jane Kangaroo , who mistrusts Horton 's inquisitive nature as a threat to her legal authority over Nool . </Li> <Li> Will Arnett as Vlad Vladikoff , a scary , savage , eccentric Russian - accented vulture hired by the Sour Kangaroo to steal Horton 's clover . </Li> <Li> Seth Rogen as Morton the Mouse , a mouse and Horton 's best friend in the Jungle of Nool . </Li> <Li> Dan Fogler as the Chairman of Whoville , dedicated to Whoville tradition and mistrustful of the Mayor . <Ul> <Li> Fogler also voices Yummo Wickersham , leader of the Wickersham ape tribe brothers . </Li> </Ul> </Li> <Li> Isla Fisher as Dr. Mary Lou LaRue , a professor at Who U . </Li> <Li> Jonah Hill as Tommy , a bear and one of Horton 's students . </Li> <Li> Amy Poehler as Sally O'Malley , the Mayor 's wife and mother to Jojo and her 96 daughters . </Li> <Li> Jaime Pressly as Mrs. Quilligan , a bird and Jessica 's mother . </Li> <Li> Charles Osgood as the Narrator </Li> <Li> Jesse McCartney as JoJo , the Mayor 's son . </Li> <Li> Josh Flitter as Rudy Kangaroo , the Sour Kangaroo 's son . </Li> <Li> Niecy Nash as Miss Yelp , the Mayor 's assistant . </Li> <Li> Laura Ortiz as Jessica Quilligan , a bird , Mrs. Quilligan 's daughter and one of Horton 's students . </Li> <Li> Selena Gomez as Helga , one of the Mayor 's 96 daughters . </Li> <Li> Joey King as Katie , a cute , but eccentric little baby yak . </Li> <Li> Bill Farmer as Willie , a bear and Tommy 's dad . </Li> <Li> Heather Goldenhersh as a Who Girl </Li> </Ul>
who is jojo in horton hears a who
Jesse McCartney as JoJo , the Mayor 's son