After seeing the sights in historical Boston, the gang is off to pay a surprise visit to Shaggy's Great Uncle Nathaniel. On the way they stumble upon The Harlem Globetrotters, who are picnicing and trying to rest up after a string of games they played around Boston. Back on the road to Uncle Nat's, Shaggy takes control of The Mystery Machine, and they begin to encounter ghosts resembling Paul Revere and soldiers of war in the road along the way. When the gangs get to Uncle Nat's, he reveals that the ghosts have scared everyone away -- and they're doing they're best to try to scare him away too. Soon the kids, Globetrotters and Uncle Nat begin running into ghosts all over the house. The following morning, everyone is on their way to a local cove when Uncle Nat tells them to keep their eyes peeled for a sea serpent that's been spotted in the lake -- subsequently Shaggy, Scooby, Meadowlark, and Curly encounter the the monster while scuba-diving. Fred and Velma come to the conclusion
Scooby-Doo and his friends give popular singers Sonny & Cher a ride after their car breaks down in a fierce storm. The kids take the two performers to the rambling, run-down Hideaway Hotel, an off-season beach retreat, where they have planned a delayed honeymoon away from the crowds. But soon, strange happenings interrupt the couple's happiness, and Scooby and the gang investigate.
When the gang find a lost dog, they return her to her owner, Phyllis Diller. They soon learn that Ms. Diller's house is haunted, presumably by the ghosts of her deceased husbands.But is it really ghosts. . .or someone trying to scare her into giving out the combination for her safe, which houses her priceless jewel collection?
When The Mystery Machine gets stuck, the gang find themselves paying a visit to nearby residents The Addams Family. But when Gomez and Morticia mistake them as the new housekeepers, the gang end up looking over the Addams home—and trying to find the missing Wednesday.But has someone kidnapped Wednesday or is the Addams home really haunted?
When The Mystery Machine breaks down (as is expected) the gang bump into smugglers (loading crates into an airplane), Batman and Robin, a little old lady, and a punching clown filled with counterfeit cash. A tip leads them to the carnival. . .where they find Joker and Penguin behind the kooky counterfeit caper. As is usually the case with these villainous villains, our heroes wind up in a funhouse hideout.