Season 1

Each episode is a self-contained story based on Dr. Seuss characters such as Yertle the Turtle and Horton the Elephant. The unifying element is that the stories are introduced and commented on by The Cat in the Hat (performed by Bruce Lanoil) who serves as host of the show. Occasionally, The Cat in the Hat himself appears in the episode, reprising his role as a bit of a trickster, as in his original eponymous books (ex. episode 1.6: "The Simplifier").

The season is notable for hewing closely to many of the themes of the original Dr. Seuss stories, with each episode possessing a strong moral overtone.

Season 2

For season 2, the show was reworked to reflect more traditional children's programming. The Cat in the Hat (now performed by Martin P. Robinson) lives in a playhouse with his Little Cats A through Z and the often flustered Terrence McBird (performed by Anthony Asbury). The Cat in the Hat is no longer a trickster and instead has assumed the role of a friendly and enthusiastic host who is helpful, nurturing and sweet. Aside from the residents of the house, there are frequent visitors based on Dr. Seuss characters.

Each episode revolves around a theme (such as family, health, art) and features one or two songs about the theme. A closing song was also added at the end of each episode. The action shifts between The Cat in the Hat and what is going on in his playhouse and shorter related story interludes, which he shows to the audience by means of his "Wubbuloscope". These story vignettes take place in various locations like:

• Seussville – a contemporary city where Sarah Hall Small and her family live.
• Jungle of Nool – a jungle that is home to Horton the Elephant, Morton the Elephant-Bird, Jane Kangaroo, Junior Kangaroo, Yertle the Turtle, the Wickershams, and the Sneels.
• Kingdom of Didd – a Renaissance-like kingdom that is ruled by King Derwin.
• Mount Crumpit – home of the Grinch and his dog, Max.

Writers hired for the season included Adam Felber and Mo Rocca. A similar episode format was featured in Jim Henson Productions' next children's program Bear in the Big Blue House , which aired on Disney Channel.

Main

• The Cat in the Hat (performed by Bruce Lanoil in Season 1 and Martin P. Robinson in Season 2) is the main protagonist and host of the series. He starts out as a trickster, then becomes a more nurturing and optimistic host.
• The Little Cats debuted in The Cat in the Hat Comes Back .
  • Little Cat A (performed by Kathryn Mullen in Season 1 and Leslie Carrara-Rudolph in Season 2) – seen as one of the Cat in the Hat's sidekicks.
  • Little Cat B (performed by Stephanie D'Abruzzo) – seen as one of the Cat in the Hat's sidekicks.
  • Little Cat C (performed by John Kennedy) – seen as one of the Cat in the Hat's sidekicks.
  • Little Cat F (performed and voiced by Pam Arciero) – seen in Season 2 at the Cat in the Hat's playhouse.
  • Little Cat N (performed by Pam Arciero) – seen in Season 2 at the Cat in the Hat's playhouse.
  • Little Cat P (performed by Tim Lagasse) – seen in Season 2 at the Cat in the Hat's playhouse.
  • Little Cat S (performed by Stephanie D'Abruzzo) – seen in Season 2 at the Cat in the Hat's playhouse.
  • Little Cat Z (performed by Anthony Asbury) – seen in Season 2 at the Cat in the Hat's playhouse. He is the smallest of all and mutters Z-words.
  • Little Cat Fleep (performed by Kevin Clash) is an indifferent little cat who only speaks in fleeps.
• Terrence McBird (performed by Anthony Asbury) is a bird that joins the main cast in Season 2. He is the cats' roommate, and is often grumpy throughout his daily activities in each episode until the end.

Supporting

• The Grinch (performed by Anthony Asbury) – he appeared in How the Grinch Stole Christmas! . He likes to dampen other people's fun and pleasure for his own vile and sadistic amusement. He serves as one of the two main antagonists of Season 1 (along with Yertle the Turtle), despite appearing in four episodes, and the main antagonist of Season 2.
• Max the Dog (performed by Kathryn Mullen in Season 1 (The Guest) and Stephanie D'Abruzzo in Season 2) – he appeared in How the Grinch Stole Christmas! . Max is the Grinch's long-suffering yet loyal dog.
• Fox in Socks and Knox in Box (performed by Bruce Lanoil in Season 1 and Tim Lagasse in Season 2 and John Kennedy respectively) – they came from Fox in Socks . Fox is lively and Knox is moody and easily annoyed.
• Yertle the Turtle (performed by Anthony Asbury) – Yertle is a turtle who tries to be king of anything, and usually uses other characters to his advantage. He serves as one of the two main antagonists of Season 1 (along with the Grinch, due to having more episodes than him), and redeems himself, becoming a recurring character in Season 2.
• Horton the Elephant (performed by John Kennedy) – he appeared in Horton Hatches the Egg and Horton Hears a Who! . He is a friendly, humble and steadfast elephant who often receives ridicule for believing in things that no one else does.
• Morton the Elephant-Bird (performed by Kathryn Mullen in Season 1 and Leslie Carrara-Rudolph in Season 2) is a Horton's half-bird son who appeared in Horton Hatches the Egg .
• Jane Kangaroo (performed by Stephanie D'Abruzzo) – she appeared in Horton Hears a Who! . She is a very snobbish and strict kangaroo who is portrayed in this series in a more sympathetic light than her book counterpart.
• Junior Kangaroo (performed by Kathryn Mullen in Season 1 and Tim Lagasse in Season 2) – he appeared in Horton Hears a Who! and is the son of Jane Kangaroo. By season 2, he and Morton have become friends.
• Thidwick the Big-Hearted Moose (performed by Anthony Asbury) is a moose who is very loving and sweet. In this show, Thidwick is also Horton the Elephant's adoptive younger brother and Morton the Elephant-Bird's adoptive uncle as seen in "The Birthday Moose". Thidwick was later dropped from the show at the end of Season 1.
• The Wickersham Brothers (performed by John Kennedy, Anthony Asbury, and Bruce Lanoil) is a family of apes who come from Horton Hears a Who! and are often employed by Jane Kangaroo and/or Yertle the Turtle.
• Sarah Hall Small (performed by Stephanie D'Abruzzo) is a girl who is a resident of Seussville. She debuted during the second season.
• Sam-I-Am (performed by John Kennedy) – he appeared in Green Eggs and Ham . He appeared in Season 2 where he would often lend a hand to the Cat in the Hat.
• Pam-I-Am (performed by Stephanie D'Abruzzo) is a female counterpart of Sam-I-Am and expert repair girl. The Cat in the Hat often summons her by calling on her on the Pam Phone, using her number's phone signals he calls "The Pam Alert", as revealed in "The Sounds All Around". Her motto is "Pam-I-Am, fix it I can!
• Matthew Katroom (performed by Anthony Asbury) is a boy who is a resident of Seussville and is good friends with Sarah Hall Small.
• King Derwin (performed by Anthony Asbury) is the King of the Kingdom of Didd who came from The 500 Hats of Bartholomew Cubbins .
• Princess Tizz (performed and voiced by Leslie Carrara-Rudolph) is the daughter of King Derwin.
• Milo (performed by John Kennedy) is a boy who resides in the Kingdom of Didd and serves as King Derwin's page.
• Norval the Fish (performed by John Kennedy) – he appeared from You're Only Old Once! Norval would appear in different roles in the show. Around Season 2, Norval would work as an advisor to the King Derwin of the Kingdom of Didd.

Minor

• Mayor Stovepipe (performed by Kathryn Mullen) is the mayor of Seussville who appeared in season 1.
• The Birthday Bird (performed by John Kennedy) appeared in Happy Birthday to You! He lives in Katroo and he likes to celebrate birthdays.
• Sally Spingel-Spungel-Sporn (performed by Camille Bonora in "The Muckster" and Stephanie D'Abruzzo in "Max the Hero" and "Horton Has a Hit") is a news reporter who came from The Cat in the Hat Song Book .
• Sue Snue (performed by Stephanie D'Abruzzo) is a girl who is a resident of Seussville and appeared in season 1.
• The Yapper-Nap (performed by John Kennedy) is a monster likes to takes nap in Seussville.
• A Snark is a pink bird that appears and lives in the Jungle of Nool. She is seen in Season 2. The Snark is a recycled version of Shirley from The Muppet Show .
• Sneels (performed by Kathryn Mullen, Heather Asch, Bruce Lanoil and Stephanie D'Abruzzo) is a race of green and pink furry creatures that live in the Jungle of Nool. They were previously used as background cave creatures in Fraggle Rock , as well as its animated series, but had different eyes here. Their babies, years after the adults debuted on the aforementioned production, also debuted here.
• Mick Maputo Bird (performed by Anthony Asbury) is an Elvis Presley-themed bird that lives in the Jungle of Nool who is also seen in season 2. He sings "Out in the Jungle" in the episode "The Cat in the Hat's Indoor Picnic".
• Lester McBird (performed by Joey Mazzarino) is Terrence McBird's twin brother who is very sensitive towards things he doesn't like and speaks in an upper English accent.

Series overview

Season 1 (1996–97)

Season 2 (1998)