I'm one of those people, I have a pelvic kidney.Passing through a scanner which shows anatomy in the wrong place (not that there aren't Humans who have this problem)?
At least with The X-Files and Supernatural there was an explanation. In X-Files I don't know if they said it specially but I had alway assumed the people's eyes turning black was literally Black Oil filling up their eyes. And Supernatural's demons were clouds of black smoke, like the Black Oil, I always assumed it was the demon smoke itself filling covering their eyes.Or showing they’ve been possessed by an aliens by having their eyes turn completely black, without any reason or mechanism given for that actually happening.