Continuity mistake: The gang emerge from the secret tunnel and find the movie crew dressing rooms. It shows one, then cuts back to the gang. Then it cuts back and suddenly another dressing room trailer appears next to the one seen moments before. (00:17:20)
Continuity mistake: Shaggy and Scooby stop to play a game of pool. When Scooby looks up and notices the ape head trophy has vanished, he has 4 of the balls by him, including the 6 ball. It cuts over to Shaggy, and he has the exact same set of balls next to him. (00:14:50)
Continuity mistake: Scooby finds a half eaten hamburger in a plate on the floor. When the camera cuts further back to show Shaggy, the plate has moved on the floor, as noted by the lines between boards and the placement of the plate and the spider web on the wall. (00:07:20)
Continuity mistake: After Candy and the stunt man quit the movie, Mr. Maxwell says he has to withdraw his job offer to the gang as it's too dangerous. As the gang is shown, Scooby is sitting in front of Shaggy and Fred. It cuts to a close up of him as he gets excited about this, and suddenly Fred and Shaggy have vanished. (00:06:10)
Revealing mistake: Scooby knocks on a trunk and it knocks back. Fred is shown and tells Scooby to open it. But in that shot, Fred's face is so badly drawn, you almost can't even tell it's him if not for the clothes and the voice. (00:05:20)
Continuity mistake: The Ape Man breaks the rope bridge that Scooby is on and it begins to fall. But by the Ape Man, the stakes holding the broken ropes are still in the ground at his feet. Scooby falls down and lands on a root, which bounces him back up where he punches the Ape Man. The stakes and broken rope have vanished. (00:03:50)
Continuity mistake: The camera pans over the filming set and stops on the gang with Mr. Maxwell. There is a van behind them with the Ape Man movie poster on the side. The vinyl piece on the side of the van goes behind the poster and is lined up directly with the orange letters saying "EPI-CENTER FILM COMPANY." It then cuts to a close up of the poster and suddenly it has moved up on the vinyl and become smaller, lined up with the underside of "LOCATION No.2" (00:01:20)
Continuity mistake: The Ape Man puts on a mask of Scooby and pretends to be a reflection. As he is mimicking Scooby's movements, he places his hand to Scooby's and his nails are sticking up. It cuts to a different angle and his hand is in a slightly different position, and his nails vanish. (00:10:05)
Chosen answer: A ghost wouldn't have to keep any food in the fridge - they don't need to eat. So it is one thing that proves the ghost is not a ghost.