Turtle is an 11-year-old girl who moves to Key West during the Great Depression because her mother's employer refuses to house children. She models her skeptical outlook on the world after comic strips like Terry and the Pirates, expecting disappointment from adults. Despite her tough exterior, she harbors a deep wish for a stable family home with her mother.

Aunt Minnie operates a home laundry business to support her three sons while her husband works construction jobs away from home. She is stressed by financial pressures and maintains a strict, sometimes critical household environment. She holds onto old frustrations regarding her sister's past actions, including a dispute over a set of paper dolls.

Sadiebelle is Turtle's mother, working domestic jobs for wealthy employers up north. She is optimistic and hopeful, frequently dreaming of buying a property from a mail-order catalog. She relies heavily on romantic partners for support and left Key West years ago after a bitter falling out with her mother.

Slow Poke is a local sailor who operates a boat called The Lost Love, making his living by harvesting sea sponges. He earns his nickname from his relaxed, unhurried approach to life and decisions. He immediately recognizes Turtle upon her arrival and treats her with generous warmth.

Philomena, known locally as Nana Philly, lives in a decaying, boarded-up house in Key West. She suffered a stroke that affected her speech and physical mobility, requiring daily assistance. She maintains a bitter, abrasive exterior, frequently knocking away the food that visitors prepare for her to test their resolve.

Beans is Turtle's oldest cousin and the strict leader of the Diaper Gang, a neighborhood babysitting enterprise that trades services for candy. He enforces rigid rules, including an absolute ban on girls joining the group. He is highly protective of his local status and resents Turtle for disrupting his living arrangements.

Kermit is Turtle's nine- or ten-year-old cousin and an active member of the Diaper Gang. He is medically required to avoid physical exertion while recovering from rheumatic fever, but he frequently disobeys his mother's orders to run and play. He is generally more welcoming and communicative with Turtle than his older brother.

Buddy is Turtle's four-year-old cousin. He is currently going through toilet training and frequently misplaces his pants, adding to the chaotic environment in Aunt Minnie's small home.

Pork Chop is Beans's close friend and a core member of the Diaper Gang. His mother cooks and sells Cuban appetizers, which he occasionally shares. He echoes Beans's exclusionary attitude toward Turtle and enthusiastically participates in neighborhood pranks.

Ira is the founding member of the Diaper Gang who recently returned to Key West. He brings fresh ideas to the group, introducing them to a window-tapping prank called tick-tocking.

Archie is Sadiebelle's current boyfriend, a traveling salesman who peddles dreams of a better life. He bought Turtle a pair of shoes before she left for Florida and constantly promises that the three of them will soon live together in a real house.

A bald traveling salesman who owes a financial debt to Archie Meeks. He repays this obligation by giving Turtle a cross-country ride to Key West, offering conversational observations along the way.

Vernon is Aunt Minnie's quiet, mild-mannered husband. He works weeks at a time on a highway project in the Upper Keys. He mends his own clothes, having learned domestic skills from his sailor father, and brings a temporary calm to the rowdy household.

Too Bad is a local boy desperate to join the Diaper Gang's ranks. During his practical audition, he forgets the cardinal rule to always duck while changing a baby, resulting in immediate rejection.

Johnny Cakes is a local merchant who illegally imports rum from the Bahamas. He owns a boat that becomes central to the children's local activities on the water.

Killie is a feeble old man targeted by the neighborhood boys' taunts. They harass him based on a local rumor claiming he once whipped a horse to death.

Miss Bea works as a daily caretaker for the elderly Nana Philly. She prepares meals for her and encourages Turtle to return for regular visits.

Ollie serves as the first mate on Slow Poke's sponge-diving boat. He assists with the daily operations on the water and helps manage the vessel.

Jelly is an elderly neighbor living across the street from Aunt Minnie. He stays highly informed about neighborhood gossip and interacts regularly with the local children.

Smokey is Turtle's pet cat, bearing singed fur from past abuse by neighborhood boys. Aunt Minnie banishes him to the yard upon arrival, but he remains a loyal companion and protector to Turtle in her new environment.

Termite is Beans's pet dog. He earns his name because he is impossible to get rid of, frequently dedicating his time to chasing the neighborhood cats.

Miss Sugarapple is a local schoolteacher who previously caught Beans and Pork Chop cheating. She becomes a primary target for the boys' nocturnal window-tapping pranks as retribution.

A famous writer living in Key West. Turtle meets him briefly and, unimpressed by traditional literature, suggests he write for the funny pages if he truly wants to achieve fame.