That sleep paralysis is the real deal from my experience. On several occasions while sleeping in my cabin I have woke up and not been able to move. Seemingly able to see, hear etc. On two occasions, one in the cabin and one while sleeping outside in the forest I found myself in this condition and was terrified to see a bear standing beside me. In the end there was no bear, but a bear is what I was worried about when I went to sleep. This seems to happen to me when I am away from home and vulnerable in some sense. The porch where I sleep in the cabin is mostly screen and not much more secure than a tent. My opinion is that most of the alien visitation phenomena can be linked to this. I was really paralyzed and really did see the bear, but the bear just wasn't there.