Caillou teases his little sister Rosie about her pacifier, not understanding why she can't be without it. After she gets upset, Mommy takes Rosie in her arms and explains that the pacifier is a way for Rosie to feel reassured and comforted, just like her blankie. Rosie wants to speak, though, and as she starts communicating and becoming more independent, the pacifier becomes less important.

Caillou is building a beautiful castle that his sister Rosie accidently destroys.

Caillou, like all children, needs to feel loved by his mother. But as a four-year-old, Caillou also has to discover the world around him. Caillou imitates the love he feels from his mother by reciting to his precious teddy bear a loving little verse his mother says to him all the time.

Caillou no longer wants to wear diapers, even at night.

Caillou enjoys playing games with his parents and listening to a bedtime story, but when it's time to go to bed, he doesn't want to sleep in the dark with the door closed.

In this lighthearted and intimate book, Caillou introduces himself and shares the details of his young life: his family, his world, his daily routine.