The tree and the tornado
We see a number of times once the poltergeist enters into the house through the TV that it is able to manipulate things and make them look real to people when they're not, which made me wonder about the occurrence of the tornado coming and sucking up the tree. Was the tornado in fact real or some sort of manipulation again? Because it seemed like it only affected them and nobody else. Also, the tree was apparently very old and had been there already for years so I guess this was just a tree being manipulated into being evil by the poltergeist, like the toys and skeletons? Perhaps this reinforces the idea of the tornado being real then, as you'd expect the tree if being manipulated to just return to its normal state, only it was sucked up permanently.
Just this aspect of the film alone kind of raises some interesting questions.