From what I can tell, Shaggy is dressed like a mummy, Fred is dressed like a pirate, Velma is dressed like a Witch, Daphne is dressed like a fairy princess, and Scooby Doo is dressed like a vampire, also the costumes that Fred, Velma and Daphne are wearing were used in a Halloween Episode of The Scooby Doo Show entitled The Headless Horseman of Halloween.
