Other mistake: When Vic and Amber are admiring their scary look in the mirror during the party, Casper's uncles appear in it as well. But we see earlier in the film that Casper has no reflection so they should have none either.
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Suggested correction: They were hiding inside of the mirror as a prank.
Other mistake: As the priest walks out of the haunted mansion with his head twisted, you can see the head and body don't step in time together.
Other mistake: When Kat chooses her bedroom in the mansion the bed should be covered in dust but it's not.
