Greg’s filmmaking partner and friend, Earl comes from a challenging background and contrasts with Greg in many ways. He provides Greg with a grounded perspective.

A girl with cancer who forms an unexpected but meaningful friendship with Greg, influencing his emotional development. Her patience and understanding help Greg connect with her.

Greg’s mom, who is actively involved in his social life, urging him to befriend Rachel. She has a strong moral sense and openly expresses her emotions.

Greg’s dad, a quirky professor known for his interest in peculiar foods and obscure films, which he shares with Greg and Earl, helping to inspire their filmmaking.

A teacher at Benson High who stands out for his genuine passion for facts and research. His unique demeanor makes him an ally for Greg during difficult times.

Rachel's mother is protective and concerned about her daughter, working with Greg’s mom to foster Greg and Rachel's friendship. She handles the difficulties of her situation alone.

Greg's longtime crush, whose actions indirectly prompt Greg to further his friendship with Rachel. Her suggestion leads to a significant turning point for Greg.

Greg's sisters, with Gretchen being the "older younger" sister and Grace the "younger younger" one, each exhibiting distinctive, quirky family traits.

The Gaines family cat, known for being philosophical and playing a minor role in Greg and Earl's films due to a lack of other participants.

Earl’s younger half-brothers whose unpredictable behavior makes visiting their home a challenge for Greg, contributing to his fear of unexpected fights.

The authoritative principal with a distinct speaking style, known for organizing school events, including a pivotal one involving Greg.