Shawn is a fourteen-year-old boy living with cerebral palsy. Because he cannot control his muscles, speech, or bowel movements, his family and the outside world assume he has the mental capacity of an infant. Internally, Shawn possesses deep intelligence and a perfect memory with total auditory recall. He frequently experiences seizures, which he cherishes as out-of-body experiences that grant him his only sense of freedom and movement.

Sydney is Shawn's estranged father, having left the family when Shawn was four due to his inability to cope with his son's severe disabilities. He is a Pulitzer Prize-winning poet who gained fame for writing verses about his painful relationship with Shawn. Deeply conflicted, self-absorbed, and prone to feeling trapped by responsibility, Sydney operates under the rigid assumption that Shawn's frequent seizures cause him unbearable physical agony.

Earl is a man serving a twenty-year prison sentence for smothering his severely brain-damaged two-year-old son to death. He is presented as a working-class foil to the highly educated Sydney. Although Earl never directly interacts with the McDaniel family outside of Sydney's interviews, his actions hang over the narrative as a dark inspiration for Sydney and a source of intense anxiety for Shawn.

Paul is Shawn's sixteen-year-old older brother. Highly athletic and prone to physical violence, he acts as the exact physical opposite of his immobile brother. He harbors a deep, stubborn resentment toward his father for abandoning their family a decade earlier. Despite his volatile nature and tendency to break household rules, he serves as Shawn's fierce, unquestioning protector.

Linda is Shawn's forty-five-year-old mother. She balances a part-time job with the exhausting, round-the-clock physical demands of being Shawn's primary caregiver. Naturally positive and fiercely devoted, she acts as the peacekeeper in the McDaniel household, continuously trying to soften the anger her older children harbor toward their estranged father.

Cindy is Shawn's seventeen-year-old older sister. She shares her mother's compassionate nature and regularly assists with Shawn's care. When they were younger, she unknowingly taught him to read by pointing out words during make-believe teaching games. She frequently hosts sleepovers with friends, inadvertently giving the silent Shawn an unfiltered window into teenage social dynamics.

William is a fifty-year-old classroom assistant in Shawn's Severely/Profoundly Handicapped Special Education Program. Big, strong, and highly capable, he once saved Shawn from suffering a cracked skull during a dangerous fall. He treats the classroom environment with practical respect rather than nervous pity.

Becky is a young classroom assistant in Shawn's special education program. She is conventionally attractive and entirely unaware that the seemingly vegetative Shawn directs intense teenage sexual fantasies toward her during school hours.

Mrs. Hare is the lead teacher for the Severely/Profoundly Handicapped Special Education Program at Shoreline. She manages a loud, chaotic classroom of incontinent and vocal students with steady, mild-mannered patience.

Ally is a teenage girl and a friend of Cindy's. She is physically beautiful and treats Shawn exactly as society dictates, speaking to him loudly and slowly. Despite her condescension, her physical presence profoundly affects Shawn, triggering deep romantic dreams and giving him a renewed desire to stay alive.

Vonda is an in-home care provider hired by the McDaniel family. Unlike Linda's attentive and constant care, Vonda is somewhat impatient and generally ignores Shawn, preferring to pass the time by painting her perfect nails.

Alice is the host of a sensationalist national talk show. She caters to a loud, uneducated audience by framing every subject in the most outrageous and controversial light possible, prioritizing television ratings over nuanced discussion.