Incompetence combined with the occasional burst of disreputable laughter makes Dirty Grandpa oddly lively for a movie that's largely terrible.

Equal parts bad and baffling, it seems to have been written and directed by alien life forms who read YouTube comment sections for a week and drew these conclusions about human behavior.

This is a movie that desperately wants to be a raunchy, politically incorrect, gross-out comedy. It gets as far as desperate.

The kind of film that, one day, De Niro's great-grandchildren will watch and wonder what all the fuss about him was.