Dr. M

Dr. M was an anthropomorphic madrill who tried to breach the defenses of the Cooper Vault on Kaine Island for years. However, the vault has proved impenetrable, leading him to construct an enormous fortress around it. With his sinister genius, Dr. M has created all manner of defenses; including a force of mutant beasts. Dr. M has a large amount of knowledge on the Cooper family. This stems from the fact that Dr. M filled the role of Bentley in Sly's father's gang, rather like McSweeny filled that of Murray.

When Sly Cooper and the Cooper Gang arrived on Kaine Island, they attempted to get past Dr. M's defenses to reach the vault. Unfortunately, his intellect proved too much for them, and they not only failed to open the vault, but also lost the Cooper cane. The Guru and Dimitri both tried to recover it, but Dr. M was able to retrieve it first, using a mutated sea creature. Later, when Penelope eliminated his air defenses, Dr. M took control of a giant whale-dragonfly hybrid to attack Sly. He revealed his history to Sly, and seemingly lost the cane. In reality, he had attached a tracking device to it, allowing him to track Sly's movements through the vault. Going after him, Dr. M and his men had a brief confrontation with Murray and Bentley; where they suffered defeat, though Dr. M continued to pursue Sly.

Dr. M later engaged Sly in a final battle, with Sly beating him to the edge of defeat. Sly then tried to convince him that not all Coopers were bad, giving him an example on how he and Bentley's relationship worked. Dr. M was confused as Sly's father was "never much of a good friend". Sly then said that all Coopers were different even if they had the same bloodline; though Dr. M refused to believe this was all true. At this time, Carmelita broke her way into the vault. Seeing how Sly and Carmelita are towards each other, Dr. M then took a shot at Carmelita Fox, only for Sly to take the hit. Carmelita then finished off Dr. M. Later, as the Cooper Vault collapsed, Dr. M refused to leave after finally seeing the Cooper treasure with his own eyes, after spending many years trying to open the vault, and thus was killed by falling stones; making all main antagonists in the Sly series of games to date defeated. Unwittingly, he facilitated Sly's relationship with Carmelita, allowing his enemy to fake amnesia.