A Night of Fright is No Delight - S1-E16
Continuity mistake: When Shaggy notices footprints in the ground in the cave, he is standing behind Velma, but in a close-up of Velma in the next shot, Shaggy has gone.
A Night of Fright is No Delight - S1-E16
Continuity mistake: When Velma tells Shaggy that they are going to follow the Phantom Shadow's footprints, her glasses have no lenses in them, but they re-appear in the next shot.
A Night of Fright is No Delight - S1-E16
Continuity mistake: When the flying uniform chases Scooby, Shaggy and Velma, the shoulder strap changes shoulder whenever the uniform changes direction.
A Night of Fright is No Delight - S1-E16
Continuity mistake: When Scooby, Shaggy and Velma go up the elevator, Velma operates it with a hand lever, but when they arrive at Cousin Slicker's room, the lever has gone.
A Night of Fright is No Delight - S1-E16
Continuity mistake: When the gang meet up and realise that all the heirs are missing, Daphne is behind Scooby, but in a close-up of Scooby in the next shot, she has disappeared.
Continuity mistake: The Snow Ghost's mask goes from being a hood type to just covering the guy's face in one shot when he's stuck in the snow.
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.