Little Billy is a young boy who is the protagonist of the novel. He tries to follow his mother’s instructions to be good but finds his life boring. He is adventurous and curious and wants to explore the Forest of Sin, but his mother has forbidden him to do so. When he finally decides to disobey her and explore the forest, his curiosity is rewarded when he meets the tiny, tree-dwelling Minpins and joins forces with them to defeat the monstrous Gruncher. The Minpins hail him as a hero, and Billy becomes a confident leader rather than the obedient little boy he must be at home. Billy does not have any siblings and never mentions having friends, so meeting the Minpins stands as a highlight in his otherwise lonely childhood. Throughout the story, Billy’s imagination and curiosity help him to grow, showing that these qualities are an asset rather than a liability.

Billy’s mother is protective of Billy and has many rules to limit where he goes and what he does. She forbids him from going into the Forest of Sin or anywhere else beyond their garden gate.