Don't Fool With a Phantom - S2-E8
Continuity mistake: In Mr. Grisby's house, Shaggy says "what a place to live," and Mr. Grisby is shown to be on the left side of him, Scooby and Velma with the crystal ball on their left. It cuts to a different angle as Velma says "it's a nice place" and Mr. Grisby is suddenly on the same side as the crystal ball with his hand on it. (00:05:30)