After 72 hrs. without sleep I begin to see dæmons hanging from the wall, ceilings and crawling along the floor. But any time I've gone without sleeping regularly I see the "Shadow People" that Tainted mentioned. I once heard a radio program(Art Bell) about them, and it turns out that some people see them without sleep depravation. Some believe them to be aleins while others claim they are spirits.

Don't know how far I've gotten off topic, but I think most of that is relevent.