Jemmy is a young boy who grew up in poverty as the son of a rat-catcher. Drafted into the royal household to serve as the prince’s whipping boy, he secretly takes advantage of the situation by learning to read and write during the prince's lessons. Stubborn and highly intelligent, he longs to escape the castle and return to a carefree life on the streets.

Prince Horace is the heir to the throne who refuses to learn his lessons or behave properly. Isolated in his life of luxury, he acts out partly due to a belief that his father does not care about him. When he decides to run away out of boredom, he is thrust into a world that tests his entitlement and forces him to rely on others.

Also known as Hold-Your-Nose Billy, he is a rough highwayman who captures the runaway boys. Illiterate and prone to relying on brute force, he sees an opportunity for immense wealth by holding the prince for ransom. He works closely with his partner to execute their clumsy criminal schemes.

Cutwater is a petty criminal and outlaw who partners with Billy. He is greedy and uneducated, frequently exhibiting nervousness and anxiety about being caught by royal soldiers. He depends on intimidation to control his captives while dreaming of a massive ransom payout.

Betsey is a young girl who travels the countryside performing with her tame bear. Generous and brave, she lives freely in nature and does not hesitate to intervene when she sees others in danger. Her deep bond with her animal companion provides her with safety and community.

Petunia is a large bear who travels with Betsey. Despite her fearsome appearance, sharp claws, and immense strength, she possesses a gentle and tame nature. She is highly obedient to Betsey and serves as a powerful protector when needed.

Captain Nips is a hardworking hot-potato seller who travels with his wagon. He represents the generosity of the common people, willingly offering transportation, food, and shelter to strangers without expecting a reward.

The King is the ruler of the kingdom and father to Prince Horace. He struggles to manage his son's notorious misbehavior and is overwhelmed by his own royal duties. His distant relationship with the prince inadvertently fuels the boy's rebellious streak.

Master Peckwit is the royal tutor tasked with educating the stubborn heir. Because he is forbidden from striking royalty, he directs his frustration and physical punishments toward the whipping boy, unwittingly providing Jemmy with an extensive education.

Smudge is a common street boy who knows Jemmy from their past days of rat-catching. He is street-smart and welcoming, running a pit at the fairgrounds where people bet on animal fights.

Johnny Tosher is an experienced rat-catcher who knows his way around the dangerous underground tunnels. He provides crucial assistance and misdirection when the boys are fleeing from their pursuers.