This is an extraordinary film. Not even kidding. Delightful, bonkers, and deeply, thoroughly weird.
The genre confusion just seems to enhance every element that's in opposition. I have no idea how it can be so creepy and funny at the same time. That is some high-level craft. Easily one of M. Night's very best movies.
It's less gimmicky and more substantive than the trailer suggests. Mostly because the brother and sister were great. (Which is good, because if you're not on board with them, the movie won't work for you at all.) It's a sweet and realistic sibling relationship that quickly becomes the heart of the story. And strangely, they out-acted the mom by a significant margin.
I think the closest thing I've seen to this, in tone, is Escape From Tomorrow