Reese is the family's impulsive, dim-witted bully who operates almost entirely on animal instinct and physical aggression. Lacking a conscience or fear of consequences, he routinely cooks up dangerous stunts and thrives on torturing his younger siblings. Despite his complete academic failure and general gullibility, Reese possesses two surprising areas of genius: a savant-level mastery of gourmet cooking and an uncanny talent for military strategy during neighborhood prank wars.

Malcolm is an angsty, self-absorbed prodigy whose life is upended when he is tested with a 165 IQ and placed in the "Krelboyne" gifted class. Rather than empowering him, his genius fuels a crippling sense of alienation, turning him into an obsessive overthinker who is constantly miserable. He desperately craves mainstream popularity and normalcy, but his own massive ego, cynical attitude, and habit of moralizing frequently cause his social downfalls.