Deenie is a seventh-grader living in New Jersey whose mother pressures her to pursue modeling due to her exceptional physical appearance. Her routine of school and friendships changes drastically when she is diagnosed with idiopathic adolescent scoliosis. She must wear a bulky Milwaukee brace for four years, an experience that challenges her internalized prejudice against physical differences and forces her to reevaluate her self-image entirely.

Thelma is a highly ambitious mother who assigns strict roles to her children, dubbing Deenie the beauty and Helen the brain. She actively manages Deenie's diet and behavior to secure a modeling career. Her intense focus on external appearance leaves her devastated by her daughter's spinal diagnosis, causing her to prioritize her own disappointment over Deenie's emotional needs.

Frank operates a local gas station and provides a calm, supportive presence in the Fenner household. While he initially lets his wife dictate the girls' activities, he steps up during Deenie's medical crisis. He insists she wear her brace and continue attending school, prioritizing her long-term well-being over temporary comfort.

Helen is a high school student categorized by her mother strictly as an intellectual. She spends most of her early scenes studying or visiting friends. Following Deenie's diagnosis, she sheds her passive role, offering practical help with clothing and defending both herself and her sister against their mother's rigid expectations.

Midge is an observant seventh-grader and a fiercely loyal friend. She demonstrates immediate acceptance when Deenie reveals her medical condition. She completely lacks the ableist prejudice that initially clouds Deenie's worldview, readily welcoming a new student with a skin condition into their social circle.

Janet is a cheerful seventh-grader who successfully secures a spot on the school cheerleading squad. She throws parties, attends school mixers, and maintains a strong bond with Deenie. Her consistent kindness provides Deenie with a stable social foundation during her physical transition.

Buddy is a seventh-grade student who plays the drums in the school band. He shows genuine interest in Deenie from the start. Unlike Deenie's fears, he exhibits no hesitation or judgment regarding her medical brace, asking straightforward questions and continuing to pursue her romantically.

Barbara is a new student who lives with a visible skin eczema condition. She is kind and helpful, stepping in to tie Deenie's shoes when the new brace restricts her movement. Her friendship teaches Deenie to look beyond physical differences.

Mrs. Rappoport is the school gym teacher. She observes Deenie's unusual posture during physical activities and proactively contacts the Fenner family, initiating the diagnostic process that identifies the scoliosis.

Dr. Kliner is a direct and observant orthopedist. He explains the reality of idiopathic adolescent scoliosis to the Fenner family and prescribes a Milwaukee brace. He acts as an advocate for Deenie's emotional state against her mother's superficial complaints.

Old Lady Murray is a newsstand operator who has kyphosis, a condition that causes a visible bump on her spine. She initially serves as a target for Deenie's fear, but eventually becomes a figure of genuine inquiry as Deenie learns about spinal conditions.

Aunt Rae is an extended family member who actively supports Thelma's superficial goals. She acts patronizingly toward Deenie and focuses heavily on acquiring clothing to mask the new brace.

Dr. Moravia is the Fenner family's primary care physician. He confirms Mrs. Rappoport's observations by having Deenie touch her toes, then refers her to a specialist.

Dr. Griffith is an orthopedic specialist who performs the X-rays that officially confirm the curvature in Deenie's spine. He outlines the general options of surgery or bracing before referring the case to Dr. Kliner.

Mrs. Anderson is the vice-principal who attempts to accommodate Deenie by offering her a spot on the bus for students with disabilities. Her use of medical labels accidentally triggers Deenie's fear of stigmatization.

Gena is a former friend of Deenie's who began wearing leg braces following an accident. She represents the social isolation Deenie fears and previously inflicted on others.

Susan is a classmate who greatly admires Deenie, even going so far as to copy her impulsive haircut. Her devotion frequently irritates Deenie.

Harvey is a popular ninth-grader whom the younger girls admire. His direct questions about Deenie's condition prompt her to deflect with sarcastic remarks.

Steve is a middle school student who attends social outings with his friend Buddy and develops a connection with Janet.

Dr. Stewart is a medical professional who oversees the uncomfortable process of wrapping Deenie's torso in plaster to create the mold for her custom brace.

Joe is an attendant at Frank Fenner's gas station. His romantic involvement with Helen leads to his termination, sparking a significant argument within the family.

Myra is a high school student who frequently hosts Helen for academic study sessions.