During a sleepover at his grandparents' seaside cottage, Caillou is excited to try swimming in the ocean but spends his time focused on the things they do differently than his Mommy and Daddy.

After Rosie unknowingly bullies Caillou, he embarks on an imagination adventure of epic proportions: confronting a Giant who shows up at an important car race and causes chaos.

Alguma coisa vai mal no reino do Arco-Íris? Não se preocupe! A bondosa Vera e seu melhor amigo realizam desejos para encontrar a solução.