Bentley is an anthropomorphic turtle: a small, upright humanoid character with green skin, a rounded turtle-like head, short limbs, and a large olive-green shell covering his back. His oversized round glasses give him a distinctly scholarly appearance. He is exceptionally intelligent, analytical, inventive, cautious, and sometimes nervous. Bentley is the Cooper Gang's strategist and technology expert, specializing in planning, gadgets, and security. He grew up with Sly and Murray in an orphanage and became Sly's closest intellectual companion.

Murray is an anthropomorphic hippopotamus with a huge upright humanoid body covered in pink skin. He has a massive rounded head, small ears, a broad muzzle, enormous hands, thick arms, and powerful legs. His enormous physique makes him the group's powerhouse. Murray is cheerful, enthusiastic, loyal, competitive, and occasionally impulsive. He prefers direct action and takes great pride in his strength. He grew up alongside Sly and Bentley in the orphanage and became the Cooper Gang's muscle.

Carmelita is an anthropomorphic red fox with an athletic humanoid build, orange-red fur, a pointed muzzle, tall ears, green eyes, dark blue hair that is long, and a large bushy tail. She wears a blue police uniform with matching trousers, gloves, boots, and belt with a yellow-orange short coat. She is disciplined, intelligent, determined, and extremely persistent. As an Interpol inspector, she is dedicated to catching criminals and is an accomplished investigator and marksman. Sly is one of her most persistent targets, creating a constant rivalry between them, although she recognizes his unusual skill.

Sir Raleigh is a very short and stout anthropomorphic frog with green skin, enormous protruding eyes, a wide mouth, and a rounded amphibian head, combined with an upright humanoid body, arms, and legs. His large hat makes him resemble a flamboyant mad bachelor. Raleigh is arrogant, greedy, theatrical, and hot-tempered. He became a pirate and established a fortified island, where he uses machinery and his knowledge of weather to create dangerous storms. He is one of the Fiendish Five and keeps part of the stolen Thievius Raccoonus in his territory.

Muggshot is an anthropomorphic bulldog with pink fur, a broad bulldog head, small ears, heavy muzzle, canine teeth, and an enormous muscular humanoid body. His thick arms, shoulders, and legs give him a deliberately intimidating silhouette, while his gangster clothing emphasizes his criminal persona. He is aggressive, boastful, violent, and obsessed with strength. Muggshot was once a small, weak dog who was bullied, so he trained himself into a physical giant and became a feared criminal. His obsession with power stems from his determination never to feel weak again.

Mz. Ruby is an anthropomorphic crocodile with dark green scales, a long crocodilian snout, narrow eyes, visible teeth, and a powerful tail attached to her upright humanoid body. Her dark clothing, purple and red accents, and jewelry complement her eerie appearance. She is secretive, calculating, intimidating, and fascinated by supernatural traditions. A practitioner of voodoo, she rules a gloomy swamp filled with strange creatures and mystical imagery. She relies on fear, mystery, and supernatural abilities rather than simple physical strength.

The Panda King is an anthropomorphic giant panda with black-and-white fur, rounded ears, dark eye markings, a broad muzzle, and a large upright humanoid frame. He wears ornate Chinese-inspired robes and a distinctive hat, giving him a dignified appearance. He began life in humble circumstances and became fascinated by fireworks used by wealthy families. After mastering their creation, he grew proud of his skill and eventually turned fireworks toward crime. He is intelligent, disciplined, proud, and resentful of those whose wealth once made him feel insignificant.

Clockwerk is an enormous mechanical owl, not an organic animal: his body is made from dark metal, gears, plates, and mechanical joints. His design retains an owl's huge angular head, hooked beak, glowing red eyes, broad segmented wings, and sharp talons, but on a gigantic, predatory mechanical body. He is patient, calculating, cruel, and obsessive. Clockwerk became consumed by jealousy of the Cooper Clan's legendary reputation and devoted himself to destroying their legacy. He eventually replaced his organic body with machinery so his vendetta could continue indefinitely.