Plot hole: Given it's a government building there's no way the ghosts could drill into the U. S. Mint and not draw security's attention.
The Scooby Doo Show (1976)
1 plot hole in The Spirits of '76
Starring: Frank Welker, Don Messick, Casey Kasem, John Stephenson
Continuity mistake: In the episode of Scooby movies where they meet the Three Stooges, Fred says that Velma is missing and they need to find her. When they go off to look for her they pass a window. Fred first, Daphne, then Velma (despite her being the one missing!), Shaggy, then Scooby.
More trivia for The Scooby Doo Show