If I'm not mistaken, the visual acuity of the eye is not straight ahead, but off to the side. For example, if you stare at the Pleiades system you can see x number of stars, but if you cast your vision slighty to the side, you can see more of the stars. This really does have implications. It is said, for example, that the only way you can see fairies is to not look straight at them.
I don't think it was a fairy, but I did once see something unusual that I could only see when I wasn't looking directly at it.
About ten years ago, when I was in college, I was working at the desk in my bedroom when I noticed a wheel of light rotating beside me. It was about two feet in diameter and fairly close to me, certainly within arm's reach. I don't think I tried to touch it, though that seems like an obvious thing to try, now that I'm writing this down.
It would disappear if I turned my head to look at it directly, and then reappear immediately as soon as I turned back to work. It was very bright and very much...there, slowly rotating in front of the radiator. There was no weird lighting in the room that could have caused anything remotely like this. I wasn't overtired and I don't do drugs; this was all in normal consciousness during (if I recall this detail correctly) the daytime. Whatever it was hung around for about twenty minutes before it faded.
It didn't feel scary or threatening. In fact, the whole thing felt disarmingly
normal. As I was studying, I had to keep reminding myself that this bizarro thing was happening right next to me. Yet the "ho-hum" feeling was very persistent and hard to break through.
I think that this was probably the paranormal-est thing that's ever happened to me, though it felt so normal at the time that I wonder if I might have had other unusual experiences that I then normalize.
I don't know if others have experienced it, but that "normal" feeling feels even more insidious than the screen memories I've heard people like Whitley Streiber talk about -- part of me worries that I might have seen a UFO and said, "Interesting. Well, I've heard they're out there, so it's not unusual that I'd be seeing one. What's for dinner?" and just moved on, letting it blend into my life so seamlessly that I'd forget I'd had an extraordinary experience. I'm pretty sure that this has NOT happened, but when you do see something so strange that you don't know how to integrate it, I think that normalizing and forgetting is one of the brain's possible ways of responding to it.