Greg's cheerful and trusting best friend, depicted with a square head and buckteeth; his playful and naive nature often makes him a target for Greg's schemes.

Greg’s dad, who threatens to send Greg to military school; he wants his sons to embody traditional masculine ideals and is embarrassed by their misbehavior.

Greg’s teenage older brother with angry eyebrows and spiky hair, who constantly bullies Greg and is more interested in his heavy metal band than academics.

Greg’s mom, who often mediates family conflicts and suggests bonding activities; she embarrasses Greg by treating him like a child and being overly sappy in public.

Greg’s toddler younger brother, who is often treated with special leniency by their parents; his naiveté and tantrums create household tension.

Greg’s classmate and crush, known as the fourth prettiest girl at school; she exhibits little interest in Greg and mistakes him for another student.

A teenager from the neighborhood whose bad behavior changed after attending military school, inspiring Frank's idea of disciplinary action for Greg.