I think the problem with Mom (1991) is that it couldn’t quite decide on its desired identity. It’s a movie about your typical grandmother being bitten by a werewolf. Is it about the horror of your mother, the grandmother of your child, becoming a ravening beast every night?
Or should the movie try to emphasize the comedic bits of a grandmother whose hunger pangs are truly embarrassing, who is herself quite embarrassed at this turn of events. There’s some amusement, for example, when she suggests that eating a homeless bum is far more acceptable than, say, a police officer.
But neither effort is pursued relentlessly, and so the movie wanders from the agony of the son, Clay, over his mother’s nightly deadly dementia, as it were, to the sight of grandma pursuing her snack of the night, an undercover cop horrified that he must shoot grandma, and frustrated that the holes he puts in her have little effect. Clay’s increasingly useless efforts to restrain his mother come to a climax when Mom eats his sister and threatens his unborn child, and so Mom must be … ah … put down.
Don’t waste your time on this one.