Under Your Bed takes a more-creepy-less-sweet approach to the very similar situation in 3 Iron, but is very good nonetheless.
While 3 Iron is near dialogueless Under Your Bed is a lot of narration with occasional interactions. I love both films despite shipping the leads in 3 Iron while standoffishly.. understanding(?) the leads in Under Your Bed. Under Your Bed is certainly a movie to watch and appreciate from a good film perspective, not one to go into expecting to be rooting for your lead character. As long as you can realize that a film can be about something bad without promoting said bad thing, I think you’ll enjoy it.