Bad, but in a good way.
But who cares when there's so much fun to be had. The two women's characters hate each other which leads to a cat-fight in the middle of a fund-raising party for the swamp where punches and cream cakes are thrown and, without them even noticing, the rest of the guests start getting eaten by monsters, following which one of them says, "I think we're alone now," and the other replies with the next line of the song. Mickey Dolenz has a surprise and funny cameo and gets (spoiler warning) eaten. Sorry was that too late? Well, it was obvious anyway. The DVD cover art doesn't exaggerate by much. There are not just two monsters but dozens of them. Most of the cast gets eaten.
It really is a bad film but I was too busy enjoying myself most of the time to notice.