This is a film about Dr. Seuss characters. It's presented by 20th Century Fox and Blue Sky Studios and narrated by Alec Baldwin.
For the first time ever, the Cat and the rest of the Dr. Seuss gang we know and love from Dr. Seuss's books will be making their big-screen debut; like they've never been seen before in a CG-Animated Feature film in 3D.
- The Cat in the Hat as Carmen, the main protagonist
- The Mayor of Whoville (Horton) as Seussville's Mayor, the duetergonist
- The Little Cats (The Cat in the Hat Comes Back) as Carmen's Sons
- Kangaroo (Horton) as Zira, the (formal) secondary antagonist
- Yertle the Turtle as Chick Hicks, the main antagonist
- Horton as Phil, the tritagonist
- Fox in Socks and Mr. Knox as Tip & Dash, two of the three tritagonists
- Wickershams (Horton) as Chick's army
- Sam-I-Am (Green Eggs and Ham) as Olaf, the secondary tritagonist
- Icchabod and Izzy (Dr. Seuss' ABC) as Tweedledee and Tweedledum
- Mack the Turtle (Yertle the Turtle) as Warp Darkmatter (Chick's formal partner), the (formal) tertiary antagonist
- Goat, Mouse, Dog Sailer, Fox, Conductor, and Passengers (Green Eggs and Ham) as the Crowd/Chorus
- The Green Eggs and Ham Characters as People drowning
- Turtles (Yertle the Turtle) as Chick's formal assistants
- ⁃ Goofy Goober - King Louie (The Jungle Book)
- ⁃ Waiter - Benson (Regular Show)
- Carmen (Moira Kelly) - a female cat who is a mother of the Little Cats
- Chick Hicks (Micheal Keaton) - a turtle and Carmen's rivial who speaks in a thick russian accent
- Mayor (Jemaine Clement) - the mayor of Seussville
- Tip (Jamie Foxx) and Dash (will.i.am) - an odd duo of animals who first met Carmen when she arrived at the beach
- Zira (Sally Feild) - Chick's henchwoman and wife
- Phil (Jason Alexander) - Carmen's college roomate and best friend
- Olaf (Andy Garcia) - Carmen's uncle
- Little Cats A (Hank Azaria), Little Cat B (George Lopez) and Little Cat C (Hank Azaria) - the 3 sons of Carmen
- Warp (Diedrich Bader) - the 3rd member of Team Chick
- Tweedledee (Kristen Bell) and Tweedledum (Josh Gad) - the people who show Carmen, Phil, Olaf, Tip & Dash the way to defeat Chick
- Chick: He and his army are in a net, pulled by Zira, Warp, his former assistants and the heroes and pushed up to the sky by Carmen. After they are in the sky, they are sent to Hong Kong by a Tramp Steamer
- Zira: Reforms
- Warp: Reforms
- Chick's assistants: Reform
- Chick's Army: Sent to Hong Kong with their boss
List of stock sound effects
Goofy holler ("Yaaah-hoo-hoo-hooey!!!")
- On the title screen (when "Carmen" appears onscreen)
- While Phil discovered the clue to help find Zira and Chick, he cuts the line of the chandelier, causing Olaf to do the Goofy holler.
- With Chick beggining to fall and the Tramp Steamer picks him and his assistants up.
- When Chick swings his sword at Carmen but he does a Tarzan yell while Carmen flees.
- the lead lets out an updated version of this yell to close out the film.
- After Phil cut the chandelier and Olaf and Phil fell in the Ground.
- After Phil and Olaf jump on a chandelier
- After the Net (with Chick and his army in it) falls
- At the beginning.