|Steve Carell||Mayor of Who-ville|
|Amy Poehler||Salley O'Malley|
|Jesse McCartney||Jo Jo|
|Isla Fisher||Dr. Larue|
|Jaime Pressly||Mrs. Quilligan|
Animated elephant Horton finds a speck of dust floating in the Jungle of Nool. Upon investigation of the speck, Horton discovers the tiny city of Who-ville and its residents, the Whos, which he can hear but cannot see. Horton forms a friendship with the mayor of Who-ville, Ned McDodd, and promises to transport Who-ville to safety. However, Horton encounters opposition from his jungle neighbors, who don't want to believe in the existence of Who-ville.