Skull is a criminal.
Insert details here.
He hates dogs, but he loves tinkering with gadgets like remote-controlled mini-cars. He has made "cool spy stuff" for Scar.
What's New, Scooby-Doo?
He was working with Meadow (the Cat Creature) to kidnap the Secret Six puppies. He and his partner Scar had with them a Great Dane that looked exactly like Scooby-Doo (other than being much fiercer and unable to talk) when they kidnapped the Secret Six. They swapped dogs and kidnapped Scooby also to avoid leaving a witness who could describe them. (The other dog was M'Lady Moonbeam in disguise, part of a last-minute enhancement to the plan once Meadow knew Scooby would be involved in the case.) He was caught and sent to prison. (Homeward Hound)