The Scarecrow escaped from Arkham again, which is generally very bad news. However, once trapped, he insists he had nothing to do with the drone attack, even though they were armed with his fear toxin. Something about the way Crane protests his innocence unsettles Velma, but she takes the bows in front of the media anyway. Scooby and Shaggy go off trick-or-treating to celebrate, but nobody initially believes them when they return to warn Crystal Cove the combination of Crane’s serum and leaked toxic waste has created an army of mutant pumpkins.
The gang must admit they were wrong to doubt when the pumpkins attack the Halloween revelers on Main Street. Soon, Mystery Incorporated and the Halloween parade grand marshal, Elvira, Mistress of the Dark, flee the mutant pumpkins in extended chase scene that nearly constitutes one third of the film.
The Scarecrow (voiced by Dwight Shultz) and Elvira (naturally portrayed by her real-life alter-ego, Cassandra Peterson) are welcome guest stars and co-conspirators in this Scooby misadventure. However, the gags involving Bill Nye the Bachelor of Science Guy fall pretty flat. Since the Mystery Machine suffers damage from the first act drone, Nye supplies a high-tech replacement that comes with his own annoying hologram.
