When I'm not getting very much sleep, I often see cats or some other small animal run in front of me out of the corner of my eye, and I turn to look and there is no sign of an animal of any kind. And today a really weird thing happened, I saw a photo of a person, and I could have sworn the person turned his head to look at me, and then I blinked and the picture was back to normal. What kind of things have you all halucinated(it can be from lack of sleep, drug use, etc.)? Also, for you super smart people out there, what causes a halucination? I'm just curious.