Watch Horton Hears A Who! Full Movie Free Online Horton the Elephant struggles to protect a microscopic community from his neighbors who refuse to believe it exists. Jim Carrey ... Horton (voice) Steve Carell ... The Mayor of Whoville (voice) Carol Burnett ... Kangaroo (voice) Will Arnett ... Vlad (voice) Seth Rogen ... Morton (voice) Dan Fogler ... Councilman / Yummo Wickersham (voice) Isla Fisher ... Dr. Mary Lou Larue (voice) Jonah Hill ... Tommy (voice) Amy Poehler ... Sally O'Malley (voice) Jaime Pressly ... Mrs. Quilligan (voice) Charles Osgood ... Narrator (voice) Josh Flitter ... Rudy (voice) Niecy Nash ... Miss Yelp (voice) Jesse McCartney ... JoJo (voice) Shelby Adamowsky ... Hedy / Hooly / Additional Voices (voice)