Alfie is a twelve-and-a-half-year-old boy whose teeth are in terrible condition due to his lifelong avoidance of dental care. Following the death of his mother and the declining health of his father, he takes on immense responsibilities at home, living in deep poverty. He loves his dad fiercely and attempts to manage the household chores while dodging the terrifying new town dentist.

Dad is a former coal miner who suffers from chronic breathing issues due to years of inhaling coal dust. Unable to work and confined to a wheelchair, he relies heavily on his young son for daily physical care. Despite his illness and poverty, he maintains an optimistic demeanor and attempts to bring magic into Alfie's life through imaginative storytelling.

Winnie is an enthusiastic, loud social worker assigned to evaluate Alfie's home life. She wears brightly colored, mismatched clothing and rides a red moped around town. Though her stated goal is to help the struggling family, her immediate focus on forcing Alfie to attend a dreaded dental appointment makes her an immediate adversary in his eyes.

Miss Root is the disturbing new dentist in town who takes over the practice of the late Mr. Erstwhile. She demands that children call her "Mummy" and distributes strange sugar-free candies that seemingly replenish themselves. With perfect teeth and completely black eyes, she takes a terrifyingly keen interest in Alfie's poor dental hygiene.

Gabz is a small, dreadlocked classmate of Alfie who is often dismissed by others as quiet or shy. She is actually highly observant and bold, tracking a bizarre string of incidents involving horrible items left under children's pillows. She quickly establishes herself as the only person at school who sees through Miss Root's cheerful facade.

Raj is the friendly, generous clerk at the neighborhood newsstand. He is one of the few adults who treats Alfie with genuine kindness without judging his poverty. Prone to giving away candy for free and sharing town gossip, he serves as a comforting presence in Alfie's stressful life.

Police Constable Plank is the town's bumbling, entirely unhelpful police officer. He prioritizes trivial issues over genuine mysteries and consistently refuses to listen to children. He frequently consumes jam sandwiches and misinterprets obvious situations.

Mr. Snood is the theatrical, black-clad drama teacher at Alfie's school. He is obsessed with improvisation exercises and views every disruption as an opportunity for his students to practice their acting skills.

Miss Hare is a science teacher whose experiments are frequently derailed by chaos. She inadvertently becomes the center of a school-wide scandal known as "Knickergate" when she slips and falls during a frantic pursuit through the hallways.

Mr. Grey is the ineffectual principal of Alfie's school. He wears various shades of gray clothing and struggles to maintain authority over both his students and the escalating chaos that occasionally breaks out in his hallways.

Fang is Miss Root's white cat. The animal is hostile and aggressive, actively hissing at patients while Miss Root falsely claims the pet is simply being friendly.