I don't know if there's a name for this, but I have a white shadow person. When I do dishes at night, and I'm tired, I can see him (or her?) standing right by the fridge. If I turn my head at the correct angle, this person appears between the edge of the white refrigerator door, and the very edge of my periphery. I don't know why this person is so interested in my dish-doing, but I try to put on a good show.
Of course, I'm being silly. If I trusted everything I saw out of the corner of my eye, I would be a very nervous person at night, when the sunlight goes away, and I'm dead tired in spite of a video game that needs to be played. I see so many little shadow dogs sitting on the floor, and shadow people sitting on the couch, and shadow creeps hiding in the laundry room, that, if I believed they were all sentient beings, I would be calling the Catholic church for an exorcism.
Our brain makes people, whether or not people are there. It's so sensitive to people, faces in particular, that it can make people out of just about anything. Without trying too hard, we can see a face on the front of a car, or a mailman in the thick needles of a fir tree, or a man riding a horse in the drywall. Not only do we see faces, we see faces with expressions. My entertainment center looks mighty surprised right now. But if I got a wider TV it might look like it was smiling.
In our peripheral vision, which is probably less detailed than you think, our brain's person-finding software is working hard to see if anyone is there, and if there is the faintest possibility that what it's seeing could be a person, it's going to show you a person. If that person is all dark and smudgy, you get a shadow person. If that person is made out of the door of a fridge, and a water cooler a few feet away, you'll get a reverse-shadow person.
This is another instance where it can be unwise to believe your own eyes. Especially the corners of your eyes, which are always a bad witness. You'd never identify a mugger by standing at a right-angle to the lineup, after all. You would never try to catch a baseball by looking to the side.
Our poor brains try their hardest to do what they can with what they have. They're the most advanced computers on the planet, but they're handling such a gargantuan heap of data every second that things do get filed into the wrong categories, and the wrong emotions get triggered, and we end up with an anomalous experience that, in the end, may have never existed outside of our own experience.
Because, in the end, everything we see, hear, feel, taste and smell depends entirely upon our brain's passive, running-in-the-background interpretation of what's going on around us. These are based on light waves, vibrating air, particles floating near our faces, and electrical signals from the skin. The closest that any of us will get to directly experiencing something is just reading the reports that our senses write out for us.
When the sense of sight tells you something, you have to take it with a grain of salt, because not only is sight a bit superstitious, but it's also perfectly confident of what it's saying. And that's always a bad combination.