Plot hole: Skipper spots the Masked Mutant's headquarters the first time he goes past. He then goes back the next day, and the headquarters have vanished. He then goes back a third time, and the headquarters aren't there yet again. However Skipper says "How can it be. It was right here yesterday," although it wasn't.
Continuity mistake: When Cara and Freddy are sliding down in the coffin, Cara is lying back for a few shots, then she's sitting up with her hands holding the sides of the coffin, then her hands are the holding the front, then they're back on the sides for two shots then when they stop, her hands are in front again.
Visible crew/equipment: In one long shot, a scarecrow is shown walking past doors and windows, trying to break into the house. As the scarecrow nears the only open-draped window, the camera operator is reflected in it. The reflection appears for a short second, only to be blocked out by the scarecrow's bulky figure.