Dictionary.com defines sleep paralysis as "A condition in which, upon waking, a person is aware of the surroundings but is unable to move." Although relatively harmless it can be quite disturbing. I havent had it happen in quite a while now, but I did just now. It used to happen in college all of the time. I would wake up and think there were people in my room, but I wouldnt be able to move or talk. Finally I would be able to and I would go around asking people if they were in my room and would say no. So, I always assumed that I had dreamt it. Until I learned it was this sleep paralysis thing. I always thought it was weird, because the room, when this happened, was always just as it was (window open, light on, movie paused), but then there was this unreal part (people in the room).
Just now, I fell asleep on the couch and upon waking, the room was just as it is, but there was this music. It was clear as day. I cant remember the words now, but it was no song I've ever heard. The scary part about the whole ordeal is that I try so hard to move and wake myself up. I will think to myself that if I could only move my left arm, I could snap out of this unmoving state. So I try so hard and nothing happens.
I was just researching it a bit and they think that this is what happens when people say they are abducted by aliens or people think they are visited by witches. It is because in this state you hallucinate. Thankfully I have never had scary hallucinations like that. Also, I was reading that 50% of people experience an episode in their life. If you have never experienced it, I hope you never will.