I used to hallucinate late at night as a young child, from ages 3-5 or so. It was something I grew out of in time, but the imagery was terrifyingly vivid. I remember one night in particular, I was heading down the hallway at about 5:00 AM to see my father off before heading back to bed. At some point my joints locked up, the walls turned to meat and a tall figure in a wide-brimmed hat approached me.
...And then it was done and I could finally move again, could finally scream.
Those incidents have always bothered me. The imagery was too vivid and too awful for the mind of a sheltered child to produce and one day it all just stopped.
Today Youtube recommended me a video about the dangers of tripping on benadryl. Apparently one oft-shared experience for abusers of the drug is an encounter with an entity they've come to call the Hat Man.
Creeps me right the fuck out.