Revealing mistake: After Mr. Maxwell says that the local people refuse to work on the movie, Velma asks why. In her close up, her right pupil is horribly misshapen. Not round, but a wobbly, almost cloud like shape. (00:01:35)
Don't Fool With a Phantom - S2-E8
Revealing mistake: When Fred makes a joke about the dummies at the end of the episode, Daphne doesn't have a neck. (00:20:55)
A Night of Fright is No Delight - S1-E16
Revealing mistake: When Scooby and Shaggy are on the bicycle with the Green Ghosts, the Ghosts' chains are missing.
A Night of Fright is No Delight - S1-E16
Revealing mistake: When Scooby, Shaggy and Velma are on the drainpipe, it breaks and throws them into a cave. But the drainpipe hits the ocean like it is glass.
Revealing mistake: After the Ape Man runs up the stairs, Fred presses the button to turn the stairs into a slide. But you can see as he moves his finger to the button, he never touches it. His finger hits the switch above the button. (00:19:25)
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)
Don't Fool With a Phantom - S2-E8
Revealing mistake: When the Wax Phantom first appears on stage, Roger Stevens, the culprit behind the phantom, can be seen at the far right of the stage, even though he should be in the Wax Phantom costume.
Don't Fool With a Phantom - S2-E8
Revealing mistake: When Shaggy has the gang look out the window and tricks them, he is talking and as his jaw moves, an extra layer keeps appearing and disappearing from his nose above the black line of the drawing. (00:17:40)
The Haunted House Hang-Up - S2-E5
Revealing mistake: When Shaggy is holding Scooby in his arms after the gang meet Asa for the first time, Shaggy's nose is missing.
Bedlam in the Big Top - S1-E10
Revealing mistake: The clown's left leg goes through the solid wood floor of the wagon as he flies into it.
Bedlam in the Big Top - S1-E10
Revealing mistake: Velma climbs the ladder without her hands grasping the rungs.
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.