Caillou is the title character of the show. Caillou was first voiced by Bryn McAuley from 1997 through 2000, then Jaclyn Linetsky in 2000 through 2003, and then, due to Jacyln Linetsky's death, Annie Bovaird from 2003 through 2009. Caillou was first shown in the episode "Caillou Makes Cookies", which aired in 1997.
He appears in MrMouser's Angry German Kid Series episode "Angry German Kid Watches Caillou Joins the Circus in Go!Animate with Bad Words".
Caillou is voiced by Tyler McAid in Episode 33: AGK VS. Caillou, and Atarster voiced Caillou in the Noah Movie: Sailor Moon's Revenge, and he'll voice him in the future videos, as well.
Tulio Sheihee's AGK Series
He was set to appear on Episode 19 as an extra character.
He appears in Episode 18 when Leopold & Noah fight against him. After the battle, Leopold took Caillou's head off and Noah kicked it like a soccer ball.
He is voiced by Atarster.