Trouble Nubble Gum (1970)

When the schoolboy Petryk takes revenge on his classmates by erasing their names from a letter, they disappear from the real world and fall into the land of Baronia. In order to save them, Petryk must change himself and reveal the secret of Baronia. Together with his friend Katya and their teacher Bo-Bo, Petryk travels to Baronia to save their friends. Petryk turns from an avenger into a hero and conquers the cruel world of Baronia.