He makes friends with Robbie, a deaf boy, and learns how to communicate using sign language.
When Mom is busy on the phone all morning and doesn't have time for Caillou he feels very left out of things. He plays with his toy phone and then talks to Grandma on the real phone. He likes talking on the phone--it makes him feel very grown up. Caillou learns there are many different ways to communicate. He makes friends with Robbie, a deaf boy he meets in the park, and learns how to communicate using sign language. After getting caught in the rain, Caillou looses his voice, but manages to find other ways to communicate until his voice comes back. Caillou wants to be taller like his friend Jim and tries to think of a way to grow faster. Mom and Dad measure him on his growth chart and show him he has grown a whole inch since last time, but that's just not enough. Later when a plumbing problem requires someone small to help out, Caillou finds out there are some benefits to being just his size.