Cast 54

1. 

   Jim Carrey

   Horton (voice)

2. 

   Steve Carell

   Mayor (voice)

3. 

   Carol Burnett

   Kangaroo (voice)

4. 

   Will Arnett

   Vlad (voice)

5. 

   Seth Rogen

   Morton (voice)

6. 

   Dan Fogler

   Councilman / Yummo Wickersham (voice)

7. 

   Isla Fisher

   Dr. Mary Lou Larue (voice)

8. 

   Jonah Hill

   Tommy (voice)

9. 

   Amy Poehler

   Sally O'Malley (voice)

10. 

    Jaime Pressly

    Mrs. Quilligan (voice)

11. 

    Charles Osgood

    Narrator (voice)

12. 

    Josh Flitter

    Rudy (voice)

13. 

    Niecy Nash-Betts

    Miss Yelp (voice)

14. 

    Jesse McCartney

    JoJo (voice)

15. Shelby Adamowsky

    Hedy / Hooly (voice)

16. 

    Jack Angel

    Old Time Who (voice)

17. Caitlin Rose Anderson

    Helen (voice)

18. Emily Anderson

    Heather (voice)

19. 

    Jan Rabson

    Town Cryer (voice)

20. 

    John Cygan

    Who (voice)

21. 

    Jess Harnell

    Another Who (voice)

22. 

    Debi Derryberry

    Who Mom (voice)

23. 

    Samantha Droke

    Hildy / Holly (voice)

24. 

    Karen Disher

    Who Kid (voice)

25. 

    Marshall Efron

    Wickersham Guard 1 (voice)

26. 

    Bill Farmer

    Willie Bear (voice)

27. Jason Fricchione

    Joe (voice)

28. 

    Heather Goldenhersh

    Who Girl (voice)

29. 

    Selena Gomez

    Helga (voice)

30. 

    Jimmy Hayward

    Obnoxious Who (voice)

31. 

    Joey King

    Katie (voice)

32. Christina Martino

    Heidi / Haley (voice)

33. Ellie Martino

    Hanna (voice)

34. 

    Laraine Newman

    Glummox Mom (voice)

35. Tim Nordquist

    Wickersham Guard 2 (voice)

36. 

    Colleen O'Shaughnessey

    Angela (voice)

37. 

    Laura Ortiz

    Jessica (voice)

38. 

    Joe Pasquale

    The Dentist (voice)

39. Connor Anderson

    Who Child #1 (voice)

40. 

    Isabella Acres

    Additional Voices (voice)

41. 

    Bob Bergen

    Additional Voices (voice)

42. Jeff Biancalana

    Additional Voices (voice)

43. 

    Madison Davenport

    Additional Voices (voice)

44. 

    Teresa Ganzel

    Additional Voices (voice)

45. Kathy Graves Toon

    Additional Voice (voice)

46. 

    Sherry Lynn

    Additional Voices (voice)

47. 

    Danny Mann

    Additional Voices (voice)

48. 

    Mona Marshall

    Additional Voices (voice)

49. 

    Mickie McGowan

    Additional Voices (voice)

50. 

    Madison Pettis

    Additional Voices (voice)

51. 

    Grace Rolek

    Additional Voices (voice)

52. Jennessa Rose

    Additional Voices (voice)

53. 

    Ariel Winter

    Additional Voices (voice)

54. 

    Fletcher Sheridan

    Jojo (singing voice) (uncredited)

Crew 55