Sleep paralysis is a curious thing. As you might know, during an episode of sleep paralysis a person is unable to move or speak, all the while being totally aware of that. If that wasn't enough, there's also an eerie twist - while being paralyzed, one might also see hallucinations, which, when seen for the first couple of times might be intensely scary. And to make it just a little bit more fun, visual hallucinations are never pleasant, merely the level of terror felt might vary. Of course, there are a couple of theories why these things happen to usually otherwise healthy people, but nobody knows for sure.