I find the alternative reality stuff disappointing too ... why can't it be real?!! Of course, in this case, they tried to fit it into our reality by saying that humans are good at forgetting, but the world being completely covered in trees overnight would be kinda hard to forget. Still, I can live with it, how else could they explain it.
Yeah exactly. And in the same reality Earth already had multiple alien invasions including the year that never was and they acted like nothing happened? Hmmm.