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.
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)
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)
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.
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.