| Cast list | | Jim Carrey | as | Horton (voice) | | Steve Carell | as | The Mayor of Who-ville (voice) | | Jaime Pressly | as | (voice) | | Isla Fisher | as | (voice) | | Seth Rogen | as | (voice) | | Will Arnett | as | (voice) | | Dane Cook | as | (voice) | | Amy Poehler | as | (voice) | | Jonah Hill | as | (voice) | | Dan Fogler | as | Yummo (voice) | | Adewale Akinnuoye-Agbaje | as | Town Crier (voice) | | Laura Ortiz | as | Jessica | | Carol Burnett | as | Kangaroo (voice) | | Josh Flitter | as | Rudy (voice) | | Shelby Adamowsky | as | The Mayor's Daughter | | Selena Gomez | as | Mayor's daughter (voice) | | Joey King | as | Katie (voice) | | Samantha Droke | as | Mayor's Daughter (voice) |
| | Crew list: | | Jimmy Hayward (Director) | | Steve Martino (Director) | | Ken Daurio (Writer) | | Cinco Paul (Writer) |
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