A kids show on PBS, based on a series of Canadian picture books. It is intended for very young children, from 2 to 4 years old (Caillou himself is four).
It is a simple animation, with the background often left blank white. Caillou and his family go on watered down adventures (train trips, making new friends).
It also has puppet shows and live people (the Caillettes sing, and there are videos of 'real kids' doing stuff) to fill in the cracks.