So back when I was a kid, my parent's room was adjacent to mine and there was an air vent connecting the rooms. When their light was on, it would cast a shadow that looked vaguely like the ghost of a tarantula, and it used to terrify me at night. I couldn't sleep without something covering my eyes and even still, I faced the other wall just to be safe. Funny thing is, I wasn't even afraid of ghosts or spiders. Just this thing.