- "Growing up is the greatest adventure of all."
- —Promotional tagline
The series has 4 seasons. The episodes started being made in 1998, some of the episodes were originally made into books which were published in 1992 and written as early as 1987. The first Caillou episode was Caillou Makes Cookies although Big brother Caillou takes place the earliest. Through out the whole series there have been many Crying Clips. By season 3 there were (and still are) 24 main characters on the show. When Caillou first came out Caillou was 3 years old. By Season 4 episodes started having Caillou imagining something at least once.
The table here shows what season the main characters first appeared in. No new characters have been added to the show since Season 3.
|Season||New main characters|
|Season 1||Caillou, Rosie, Caillou's Mommy, Caillou's Daddy, Leo, Clementine. Grandma, Grandpa, Julie, Sarah , Andre, Gilbert, Ms.Martin, Mr. Hinkle, Gilbert, Deedee, Rexy, Jim|
|Season 2||Jeffery, Jason, Billy|
|Season 3||Jonus, Emma, Xavier|
Listed here are characters that are no longer on the show and why.
- Deedee - Last appeared in Season 1 when the Puppet segments ended
- Rexy - Last appeared in Season 1 when the Puppet segments ended
- Teddy - Last appeared in Season 1 when the Puppet segments ended
- Julie - Last appeared in Season 3, probably couldn't babysit Caillou anymore or got too busy
- Jim -Last appeared in Season 3, probably stopped because he got too old for Caillou or moved away