Gilbert is Caillou's pet cat. He has gray fur and a blue spot over one of his eyes. He has been on the show since Season 1; he likes playing with Sarah's cat Olly. Gilbert also appears in the puppet segments of the show, too. In the puppet segments he talks but in the regular episodes he does not. Gilbert likes playing with Sarah's cat Olly. He hates the bulldog in the neighborhood.
In the episode Caillou's new member of the family in season 3, Caillou, Rosie and Mommy are looking at old picture. They saw one when Gilbert was a kitten and Caillou remembers when the family got Gilbert.