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I watched this movie around 80s to 90s.
I remember the part about a monster creature, who wore a wedding dress and was about to marry the kid's dad. She changed her skin from a kind of green lizard-like or alligator-like but little creepy into human skin. Some kids found out this woman is not human; he tried to tell his father about it but he don't believe him.
Some kids went to the cave to free some people whom she had kidnapped.