Shaggy is trick-or-treating when a rude man at the door takes Shaggy's bag and throws it over him violently enough to tear a hole for his head. Later, Arlene encounters Shaggy and Scooby on the streets as a mob chases her. Shaggy is still holding his bag, and the hole has vanished.
At first the sign over the cemetery gates is spelt correctly, but after Scooby and Shaggy are captured it changes to cemetary and remains that way.
When Velma says, "Hey! Look at this!", regarding one of the books in the museum, it appears to the viewers as if the pages are blank. When the camera pans to Velma's perspective, however, the book gains ornate writing, and a depiction of the symbol found on Milissa Wilcox' grave.
The story perpetuates the common misconception that the alleged witches of Salem were burned at the stake in the European fashion. In fact, they were hanged, except for a few that were crushed with rocks.
The date of the Salem Witch Trials is given as the 1770s. In fact, the final phase of the trials happened in 1693.
What century do the Salemites think they are living in? Their behavior, speech, mannerisms, and attitude about witches, are greatly exaggerated to resemble 17th-century Puritans.
Salem is depicted as a rural, wooded area, but in reality, it had become a well-populated small city by the 1970s.
Why would 18th-century torture instruments in a museum display be fully functional?
Gar tells Arlene to flee from the angry mob. She proceeds to open the front door and runs out at full speed. If the mob will be at her house "in any second", wouldn't it have been much safer to turn and run out the back door?
It seems very odd that the generic witch costume that Shaggy brought with him for Scooby to trick or treat in happens to be a carbon copy of the costume worn by the villain. Later, a mannequin in the Salem Witchcraft Museum can be seen wearing the exact same costume.