Howling VI: The Freaks

Revealing mistake: When the devil man (Bruce Payne) comes up from under his couch in his caravan, and pushes the mayor through the ceiling - they make no attempt to hide the fact that it is a dummy and its hands are gripping some special handles.

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Revealing mistake: When the hero is first caged after being captured, you can see him grab the top of the bars in his cage but when they bend (because they are rubber) he quickly lets go.