Leo, Caillou’s classmate, is always dreaming up grand adventures — Leo and Caillou could stay out playing astronauts in outer space or explorers in the thick of a jungle forever! Leo started out as a bully in the 1999 episode "Caillou Goes To Daycare", but quickly befriended Caillou in the same episode. Leo is four years old like Caillou. They've been inseparable since. According to Caillou's Holiday Movie, Leo is Jewish and celebrates Hanukkah. In one episode, Leo's mother is Mrs. Martin, the teacher at day care, though in others his mother is a different woman.
Clementine, who is 4 years old like Caillou, is essentially fearless and shares her discoveries with him. Clementine was the first to befriend Caillou in the 1999 episode "Caillou Goes To Daycare". Clementine is four years old like Caillou and Leo and can get rather bossy sometimes, but all in all she's pretty understanding. Clementine is of Black Canadian heritage.
Sarah, Caillou’s neighbor, gives Caillou a glimpse of some of the things he will be able to do when he is a little older. Caillou is eager to grow up to learn to read and write… and lose his baby teeth! Caillou first met Sarah in Caillou episode named "Caillou Goes Round the Block". She is eight years old and already attends school. Sarah is of Chinese heritage and celebrates Chinese New Year. Sarah has a cousin in an episode where she invites Caillou to celebrate Chinese New Year, but in another, where she invites him to school for "Bring Your Younger Siblings To School Day" she says she's inviting him because she has no siblings.
Paul Hinkle (French name: Monsieur Lajoie)
Paul Hinkle is Caillou's neighbor, introduced in the 1998 episode "Caillou's Not Afraid Anymore". Paul Hinkle has gold teeth.
AndrÃ© is a redheaded boy who is six. AndrÃ© is introduced in the Caillou episode "Caillou's Big Friend". AndrÃ© is clumsy and Caillou didn't like him at first, but soon became friends. According to the song "Days of the Week" released on the Caillou music CD "Caillou and Friends", Caillou plays with him every Saturday. AndrÃ© enjoys biking and soccer.
Julie is Caillou's babysitter. Julie is 15, blond, and enjoys playing with Caillou. Together, Julie and Caillou are like brother and sister, enjoying times together.
Mr. Washington is a bus driver. Apparently, the same driver that drove the bus Caillou's dad rode to school many years ago.
Jason & Jeffrey
Jason & Jeffrey are identical twins. They enjoy eating pizza. Initially, Jason & Jeffrey wore identically colored clothes. By Caillou Season 4, though, Jeffrey started wearing a shirt with inverted colors, in order to tell them apart. Jason & Jeffrey are both in Caillou's playschool class.
Billy is Clementine's older brother. He is usually seen playing in a band with his friends or playing in sports. Billy’s age is unknown, but he appears to be at least 12 years old.
Ms. Martin is Caillou's teacher. Ms. Martin has red hair and always wears overalls. According to Caillou episode ‘A Surprise For Ms.Martin’, her birthday is in June. In Caillou episode ‘Caillou goes to daycare’, it is said that Ms. Martin's first name is Ann.
Emma is a kid in Caillou's playschool class who hates loud noises.
Xavier is a kid in Calliou's playschool class. At his birthday party, Xavier had a piÃ±ata.
Jonas is Caillou's Father's friend who owns a farm with horses named Ginger and Blackie. The farms’ busiest time is Christmas because Jonas grows Christmas trees. Jonas marries Kristin on the farm with Caillou as the ring bearer and Rosie as the flower girl.
Caillou - Fan website for Caillou children’s TV show - Kayu