Greg is a seventeen-year-old senior at Benson High School in Pittsburgh who actively avoids deep social connections. He maintains a surface-level, friendly detachment from every clique to protect himself from social politics and awkward interactions. In secret, he makes low-budget parody films with his co-worker Earl, refusing to show them to anyone else. His strictly controlled routine breaks down when his mother forces him to befriend a classmate recently diagnosed with leukemia.

Earl is a high school senior who comes from a low-income household heavily affected by gang activity and an absent father. He meets Greg in kindergarten, and the two bond over video games and a shared love for obscure cinema like *Aguirre, the Wrath of God*. Earl frequently uses profanity and a gruff exterior to protect himself, yet he possesses sharp emotional intuition. He serves as Greg's creative partner while frequently calling out his friend's secretive behaviors.

Rachel is a senior at Benson High School who finds herself thrust into sudden illness. She initially rebuffs Greg's awkward attempts to hang out but eventually allows him into her life because he makes her laugh. She is observant and patient, often letting Greg do all the talking to ease his anxiety. Her quiet acceptance of her medical condition contrasts sharply with Greg's frantic attempts to control his environment.

Marla is Greg's mother and a loving woman who runs a Jewish nonprofit organization. She operates with a rigid moral compass and feels strongly about enforcing what she believes is the right thing to do. Her insistence that Greg reach out to Rachel acts as the primary catalyst for the entire story.

Victor is Greg's eccentric father and a professor of ethics. He spends his free time purchasing obscure specialty meats, watching foreign films, and having long philosophical conversations with the family cat. He plays an instrumental role in Greg and Earl's friendship by introducing them to Werner Herzog films and providing them with video equipment.

Mr. McCarthy is a young teacher at Benson High School known for his tattooed forearms and occasional habit of teaching barefoot. He stands out from the rest of the faculty by maintaining a genuine excitement for facts and research. He provides Greg and Earl with a safe haven during lunchtime and actively tries to support Greg academically.

Denise is Rachel's mother, forced to manage her daughter's sudden leukemia diagnosis on her own. She is fiercely protective of Rachel and takes an aggressive approach to securing emotional support for her child. She coordinates with Marla Gaines to arrange Greg's visits, hoping his sense of humor will provide a necessary distraction.

Madison is widely considered the most attractive girl at Benson High School and is Greg's long-standing crush. Unlike stereotypical popular girls, she is sympathetic and kind-hearted, showing genuine concern for Rachel's well-being. Greg's lingering guilt over insulting her in elementary school complicates his current inability to form coherent sentences in her presence.

Gretchen is Greg's fourteen-year-old sister. Greg avoids her carefully, noting that her teenage hormones make her temperament highly unpredictable. She often clashes with her parents, particularly acting repulsed by her father's odd dinner table antics.

Grace is Greg's six-year-old younger sister. She aspires to be a writer and a princess, frequently mimicking her father's peculiar habit of treating the family cat like a human being. She occasionally acts as a reluctant extra in Greg and Earl's amateur films.

Cat Stevens is the Gaines family cat. He enjoys eating questionable meats with Victor and tolerates being used as a prop in Greg and Earl's low-budget films. He functions as a sounding board for Victor's lengthy intellectual meditations.

Maxwell is one of Earl's younger half-brothers. He contributes to the highly combustible environment of the Jackson household, where physical altercations erupt frequently and without warning.

Brandon is Earl's other younger half-brother. Like Maxwell, his volatile temper requires guests to remain constantly alert and ready to escape the house at a moment's notice.

Principal Stewart is the highly authoritative head of Benson High School. He maintains a staccato speaking style and a perpetually angry facial expression, effectively controlling the chaotic student population.

Leah is a former Hebrew school classmate of Greg and Rachel. She is a firm feminist with multiple facial piercings and a shaved head. During middle school, Greg primarily hung around Rachel in a failed attempt to get Leah's attention.