Jack is a 17-year-old popular junior at Martin Van Buren High School. He secretly has prosopagnosia, a neurological disorder that prevents him from recognizing faces. This condition causes severe social anxiety, driving him to rely on his outgoing jock persona and easily identifiable physical traits to blend in. He works at his family's store, Masselin's Toys, and frequently builds robots in his basement as a way to control his environment.

Libby is a 16-year-old junior returning to public school after years of homeschooling. Following a severe panic attack that required her to be lifted from her bedroom by a crane, she gained public notoriety as "America's Fattest Teen." She possesses a confident exterior and a deep love for dancing, though she battles private insecurities about how her peers perceive her.

Caroline is a conventionally beautiful student at Martin Van Buren High School. She uses passive-aggressive tactics, backhanded compliments, and gossip to maintain her social status. She deeply resents anyone who threatens her position at the top of the high school hierarchy, masking her own insecurities through cruelty.

Dusty is Jack's 10-year-old younger brother. He is confident and entirely unconcerned with social norms, happily carrying a purse to his first day of school despite the potential for bullying. His strong sense of self deeply impresses Jack, who struggles with his own identity.

Will is Libby's single father. He shares a loving bond with his daughter and supports her fiercely. He often takes the brunt of public criticism regarding Libby's past health crises but remains a gentle, consistent, and protective presence in her life.

Kam is one of Jack's closest friends at school. A popular jock, he frequently instigates cruel games, prioritizing high school status over kindness. He initiates the targeted harassment against overweight girls in the cafeteria, utilizing cruelty as a form of social self-defense.

Bailey is an earnest, kind-hearted student at Martin Van Buren High. She recognizes Libby from their elementary school days five years prior and quickly rekindles their connection to offer genuine, judgment-free friendship.

Iris is a student who becomes the initial target of the "Fat Girl Rodeo" orchestrated by Jack's friends. She finds a supportive ally in Libby after the incident, though she remains hesitant to report the bullying to school authorities.

Marcus is Jack's 16-year-old brother. He is positioned to eventually take over the family business, Masselin's Toys, when he grows older. He maintains a fairly standard presence in the busy Masselin household.

Nate is Jack's father, a cancer survivor, and the owner of Masselin's Toys. He hides a personal secret from his wife that Jack accidentally discovers, creating quiet tension and resentment between father and son.

Susan is Jack's loving but no-nonsense mother. She manages the household while remaining completely unaware of the underlying tensions and hidden secrets existing between her husband and her teenage son.

Reed is a student at Martin Van Buren High. He holds a grudge against Jack following an incident at a party where Jack, due to his hidden prosopagnosia, accidentally kissed Reed's girlfriend.

Heather is the coach of the Damsels, the high school's drill team. She oversees the application and tryout process that Libby desperately wishes to participate in.

Mr. Levine is the school counselor who leads the daily Conversation Circle. He creates a structured space for students to discuss their conflicts, share their personal histories, and practice empathy.

Monica is Jack's advanced chemistry teacher. Her presence creates significant tension for Jack due to a private matter involving his father, causing the teenager to abruptly drop her class to avoid seeing her.

Moses is a persistent bully known alongside his brothers as the "James Gang." He has targeted Libby with cruel comments about her physical appearance since they were children, representing the stereotypical aggressive male bully.

Rachel is Libby's long-time therapist, tutor, and former caregiver. She provides Libby with consistent emotional support and advice, helping her transition back into public school life.

Seth is a popular student and one of Jack's best friends. He encourages toxic behavior among his peers and introduces the concept of the "Fat Girl Rodeo" game to the group.

Kendra is Caroline Lushamp's best friend and sidekick. She participates in spreading gossip and leaving passive-aggressive comments targeting vulnerable students.