Leon is the son of Theo and the father of Nana. He used to travel around Italy with his father and daughter. Unlike his father, Leon is completely uninterested to become a puppeteer. He always wanted to become a doctor since childhood. Leon used to argue with his father because of this. The determination of Leon to become a doctor became stronger after his daughter, Nana, got very sick (His daughter was cured however.). In his last and worst argument with Theo, Leon told again his father that he wants to be a doctor. He also added that he wants to help the children going through what Nana went through. All of these words angered Theo. He told Leon to leave afterwards. After the last argument, Leon left his family.

Leon went to Milan and studied to become a doctor. Professor Casella became his teacher. Few years later, Leon, who is now a doctor that treats poor children in Milan, was reunited with his father Theo and daughter Nana. Dr. Leon and Theo reconciled with each other.