Caillou is the 4-year old boy and main protagonist of the TV series of the same name. He is inquisitive, adorable, curious and his interests include cars and dinosaurs. Interestingly, Caillou was 2 ½ years old when his baby sister Rosie was born, a 3 year old for the first 18 episodes of Season 1, and after the episode "Caillou's Birthday" he turns 4 years old and remains this way for the rest of the series. He lives in a 2 story blue house on 17 Pine St. (as mentioned in the episode "Where I Live") with his father Daddy, his lovely mother Mommy and his cute and very pretty 2 year old little sister, Rosie. Later installments show him attending preschool.
In the earliest episodes, he is normally seen wearing a red sweater with green pants held up by yellow suspenders. In "Big Brother Caillou" he wears a yellow T-shirt and red overalls. Beginning with either "Caillou All Alone" or "Caillou Tidies His Toys" (depending on the episode order) he wears a greyish-beige T-shirt with a bright red collar, blue long shorts, yellow high socks and blue and red hi-top sneakers without laces. In Season 2 and the remainder of the series he wears a yellow shirt with the same red collar, but the rest of his clothing remains unchanged. It is possible that he also wears diapers or training pants in the former two outfits mentioned as evidenced by a thick round shape under his pants in some shots.
Caillou appears in all 229 Calliou episodes and has been voiced by Bryn McAuley (1997-1998), Jaclyn Linetsky (2000-2003), and Annie Bovaird (2003-present).