This one happened to me and my dad about 10 years ago, back when I was little. He already wrote something about it on Reddit quite a while ago so here's what he wrote (his point of view:) "I experienced a similar phenomenon in my daughter's bedroom. I noticed a weird shadow in the corner of her room that was never there before. It was an odd dog-shaped shadow (like the head and shoulders of a German Shepherd). After tucking her in at night, I noticed it. At first I paid very little attention to it. Then two nights later, I was driven to try and find the source of the new shadow. I turned off lights, put my hand in front of the venetian blinds over the window; I examined ambient light sources. Nothing I did affected the shadow, or allowed me to trace its source. It was bizarre. But I still wasn't terribly spooked. Then one night, I found myself sleeping in my daughter's bed (after her brother kicked me out of my own bed, subsequent to snuggling in between my wife and I.) My daughter was away with her grandparents camping, so I took her bed. At around three in the morning, my foot brushed the wall (near the shadow). For some reason, my body recoiled--as if some instinctive, visceral impulse was telling me not to touch it. It was so jarring that I woke up a little bit. Only after that did I become more suspicious about the strange new shadow. I felt as if my subconscious (but no: not my subconscious. Something deeper and more primitive) was warning me about its true nature. I almost instantly dismissed this paranoid thought. But it resurfaced the next night, when my daughter came home and I was tucking her in. She said apropos of nothing, "Have you noticed that shadow there? The one in the corner? I've never noticed it before. But it's been here since last week." I was stunned that she, too, had recognized that it was new. (Like myself, she couldn't determine its source.) It was just suddenly . . . there. I carried out my duty as a parent and pretended as if it was nothing. Just a trick of light, I said. I paid it no more attention, and encouraged her to do the same. Then a few nights later, I was unsettled yet again, when, just as mysteriously as it appeared, it vanished. No furniture was different in her room. Same venetian blinds. Same light fixtures. Same everything. But now suddenly, the shadow was gone.
What the hell was it? What created it? Why did my body (quite apart from my conscious mind) recoil when my foot brushed it? I'm a grown-ass man and I'm still perplexed by it."
It creeped me out as a kid and I knew that it wasn't light tricks, I remember trying to do the same thing he did and nothing had happened to it. The bizarre thing was it's shape; as mentioned earlier, it was shaped like the head and shoulders of a German Shepard and it was about 4 feet tall, seeming to be somehow projected from the corner of my bed tucked into the corner of the wall.