Tom is a 12-year-old boy attending the elite St. Willet's Boarding School. He is timid, unassertive, and deeply lonely, seeing his wealthy parents only during school breaks. After arriving at Lord Funt Hospital, he finds himself placed in the children's ward under strict rules. Desperate for connection, he forces his way into a secret group of young patients who sneak out at night.

He is a hospital porter with visible physical differences, including a lopsided face and a distinct limp. Abandoned at Lord Funt Hospital as an infant, he grew up in the wards and now secretly lives in the basement. Despite a daunting exterior that frightens new patients, he quietly facilitates the gang's elaborate dream-fulfillment scenarios.

Matron is the tyrannical manager of the children's ward. She appears polished from a distance but reveals a cruel, bullying nature up close. She enforces miserable conditions, forces boys into frilly pink nightgowns, and confiscates food. She openly relishes the power she holds over vulnerable children.

Sally is a 10-year-old patient and the sickest child on the ward. Prolonged medical treatments have left her weak and without hair, fueling her anxiety that she might never grow up or leave the hospital. Despite her physical frailty, she possesses sharp intelligence and a hopeful spirit.

Amber is the bossy, self-appointed leader of the Midnight Gang. She sustained multiple broken bones after falling from a top bunk bed. Despite her immobility, she directs the group's nightly operations with authority and determination. She dreams of traveling to the North Pole as an explorer.

Robin is a 12-year-old patient recovering from eye surgery. He relies on his hearing and enjoys classical music, keeping CDs near his bed. He utilizes a sharp, sarcastic wit to comment on the antics of his fellow patients and hospital staff.

George is an 11-year-old patient recovering from a tonsillectomy. He constantly sneaks sweets and chocolates into the ward, speaking with a heavy cockney accent. He serves a crucial role in the gang's escapes by lacing his candy with his prescribed sleeping pills to incapacitate the staff. His ultimate dream is to fly.

Doctor Luppers is an awkward and bumbling physician at Lord Funt Hospital. He is overly concerned with bureaucratic procedures, struggling with a ridiculously long admission form. He worries constantly about receiving positive patient ratings.

Nurse Meese is a brisk, bossy medical professional at the hospital. She values efficiency above all else, showing little bedside manner when handling new patients.

Mr. Thews is the strict headmaster of St. Willet's Boarding School for Boys. He maintains total authority over his students through intentional cruelty and restrictive rules.

Raj is an affable local newsagent who supplies George with contraband candy. While hospitalized for a minor injury, he continuously wanders the halls looking for elaborate Indian takeout orders.

Dilly is a perpetually grumpy hospital cleaning woman. She works while smoking an ashy cigarette and performs her housekeeping duties quite poorly, leaving areas dirty while remaining highly suspicious of anyone roaming the corridors.

Nelly is a 99-year-old hospital patient living with dementia. She firmly believes she is a young girl waiting for her father to arrive. Her unexpected energy throws a major wrench into the gang's carefully laid plans.

Sir Quentin Strillers is the hospital principal of Lord Funt Hospital. He is an officious administrator heavily focused on budget cuts and enforcing strict institutional rules, frequently punishing staff for minor infractions.

Tootsie is the hospital's food service worker. Despite having almost nothing to serve due to severe budget cuts, she maintains an incredibly warm and optimistic demeanor, attempting to make the children's miserable meals feel special.

Mr. Cod is the elderly pharmacist at Lord Funt Hospital. He strictly guards the medical supplies and is quick to notice when something is amiss with a prescription request.

Professor Pigeon is a one-winged bird living secretly in the hospital basement. The pigeon serves as Porter's only companion in his isolated living quarters.

Mr. Carsey is the games teacher at St. Willet's Boarding School for Boys. He is responsible for transporting Tom to Lord Funt Hospital after the cricket accident.