Continuity mistake: In the picture of Morgan Moonscar in Simone's book, his scar is much longer than it was when we saw his ghost, and also later when we see his Zombie.
Continuity mistake: When Shaggy and Scooby are walking down the airport, the suitcases in the background change between shots.
Continuity mistake: One of the cat creatures rips Shaggy's shirt at the end, but a few seconds later his shirt is fine.
Continuity mistake: In the opening shot of Velma's bookstore, there are three books in one of the piles. She then places three more books on the pile, and carries them over to a table. In this shot there are well over six books in the pile.
Continuity mistake: During Semone's story, when the moonlight flows through the opening in the ceiling, between shots the opening goes from having four horizontal bars and three vertical bars to having five horizontal bars and seven vertical bars.
Continuity mistake: During Semone's story, the position of the bandages wrapped around Morgan Moonscar's leg change significantly between shots.
Continuity mistake: Fred falls into the secret passageway while carrying a lantern with him. In a few later shots of him on the ground, the lantern is gone.
Continuity mistake: Daphne falls on Bo face up, but a few seconds later she is face down.
Continuity mistake: When the gang first drives up to the house, there are no cats on the front porch. Then a few seconds later, as Fred points out, "this place is crawling with cats".
Continuity mistake: In the scene where Shaggy and Scooby are stuck in the pit with Morgan Moonscar's zombie, the amount of rust on his sword changes between shots.
Continuity mistake: The boss enter the storage room carrying the clipboard in his left hand. In the next shot, when Shaggy says "Like, hi boss" it's in his right hand.
Continuity mistake: After Jacques tells Dalphne that there have been no survivors from the island and she replies "So we understand" her hands magically appear on the steering wheel between shots.
Continuity mistake: Between shots of Scooby sniffing the cat food, the things in the cupboard behind him change.
Continuity mistake: At the start of the opening scene, the moat monster is revealed to be Mr. Beeman, and when he shouts, "I would have gotten away with it if it wasn't for that big dog and you meddling kids," in this overhead shot, Scooby's paws are bare. In the next shot, the moat monster's mask is suddenly over one of his paws.
Continuity mistake: When Scooby is chasing the cats, he gets stuck in a log that has a hole in the top. This hole disappears a few seconds later.
Audio problem: When the alligator bites on the fisherman's pole, the sounds heard don't match it biting on it.
Continuity mistake: When Mystery Inc. visits the fortune teller, the pedestal the crystal ball is on changes from grey to brown.