Based on the books by Hélène Desputeaux,[1][2] it focuses on a four-year-old boy named Caillou who is fascinated by the world around him.

[4] Caillou lives with his family (his mother Doris, father Boris, younger sister Rosie, and pet cat Gilbert).

Caillou (voiced first by Bryn McAuley from 1997 to 2000, then Jaclyn Linetsky from 2000 until her death in 2003, and then Annie Bovaird from 2003 to 2010) meaning pebble or stone in French (nicknamed by himself The Prince of Imagination),[5] is the title character of the show.

Caillou is an imaginative four-year-old[6] boy with a love for forms of transportive machinery such as rocket ships and airplanes.

New character redesigns were handled by Travis Cowsill, a storyboard artist on Timon and Pumbaa and Invasion America.

[21] Caillou initially received generally positive reviews from television critics and parents of young children.

"[22] The New York Times wrote "Caillou looks at the world through the eyes of its 4-year-old namesake [and] takes life's not-always-so-simple lessons and presents them in a way preschoolers can understand,"[23] while Lynne Heffley of the Los Angeles Times wrote that "each animated episode is an unusually realistic reflection of a preschooler's daily fun, family interaction, challenges, disappointments and misunderstandings as Caillou grows and learns to make sense of his world", also describing it as "a virtual guidebook for parents and caregivers".

In a National Post column, writer Tristin Hopper identified Caillou to be "quite possibly the world's most universally reviled children's program."

A common criticism towards the series is that the titular character behaves like a spoiled child and suffers no consequences from his parents for his behavior.

There are no veiled math problems, spelling lessons or morality tales; it's just calm, non-threatening, bright-coloured people navigating everyday tasks."

While Sprout rebranded into Universal Kids on September 9, 2017, the show remained on the channel until it was taken off the line-up at the beginning of April 2019.

[33] Deadline Hollywood reported that many parents and viewers celebrated the news of the cancellation, as they have complained that Caillou had taught their kids bad lessons and encouraged them to be bratty and whiny.

In 2003, an album titled Caillou's Favorite Songs was released by Kid Rhino under the Cinar Music imprint.

[45] In June 2022, WildBrain announced they teamed with Comcast's streaming platform, Peacock, to produce a new series of the show, consisting of 52 11-minute episodes to go along with those specials.

[47] The first special: Rosie the Giant, which focuses on the effects of bullying, simultaneously premiered in Canada and the United States on Family Jr. and Peacock respectively on July 10, 2022.

[48] The second special: Adventures with Grandma and Grandpa, which focuses on Caillou visiting his grandparents for a sleepover at their beach house, premiered on Peacock on August 25, 2022.