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Hans Conried as Narrator / Horton / Dr. H. Hoovey (voice) |
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June Foray as Jane Kangaroo / Mother Who / Baby Who / Cindy Lou Who (voice) |
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Chuck Jones as Junior Kangaroo / Various Whos / Quizmo McKwoff / JoJo (voice) |
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Thurl Ravenscroft as Wickersham Brother (voice) (uncredited) |
| Directing | Chuck Jones | Director |
| Writing | Dr. Seuss | Teleplay |
| Production | Dr. Seuss | Producer |
| Visual Effects | Irven Spence | Animation |
| Art | Philip DeGuard | Background Designer |
| Art | Irv Wyner | Background Designer |
| Visual Effects | Phil Roman | Animation |
| Visual Effects | Ben Washam | Animation |
| Visual Effects | Carl Bell | Animation |
| Visual Effects | Tom Ray | Animation |
| Art | Angel Esparza | Background Designer |
| Sound | Eugene Poddany | Music |
| Visual Effects | Richard Thompson | Animation |
| Production | Chuck Jones | Producer |
| Art | Maurice Noble | Production Design |
| Visual Effects | Hal Ambro | Animation |
| Visual Effects | George Nicholas | Animation |
| Visual Effects | Don Morgan | Layout Supervisor |
| Art | Don Foster | Graphic Designer |
| Writing | Dr. Seuss | Book |
| Directing | Ben Washam | Co-Director |
| Editing | Jim Faris | Editor |
| Production | Earl Jonas | Production Manager |
| Art | Chuck Jones | Storyboard Artist |
| Art | Bob Ogle | Storyboard Artist |
