Case 2: You hear a growl in a lucid dream and when you focus on it you see a black dog. You come across another person's experience and compare it with yours and find it exactly similar, the same black dog. Then you read about thousands of experiences similar to your own. The question is why the black dog? You can answer this question by simply saying it is a shared archetype, alright good theory (the jungian collective unconcious is just a theory). But what if there is a conciousness that resides in a realm that has access to your dreams and wants you to see it that way, like some sort of hypnotic suggestion but in the non-physical realm? What if the hat is just another such mental suggestion?
Jungians can claim that the "hat" is a modern archetype. But to me it is something more. I would call the "hat" a distraction. I believe that the hat is an attempt to shift the human conciousness in masses. (No offence to new-agers).
Both examples are plausible. There's no doubt that our minds fill in the blanks when we can't use our five senses. For instance, I heard a very strange growl one night. It was different than anything that I heard in the past, from a factual animal or a fictional character. I could not match it to anything. For some reason, the Gill Man popped into my head. I didn't see the source of the sound, but it admittedly startled and threatened me. It seemed quite malevolent. It likely was an animal from the neighborhood that was up to no good that late at night. It's doubtful that it was a creature from a black lagoon. Still, my mind immediately went there. I would be surprised if more than a dozen or so people experienced this exact event during the past hundred years. It likely was particular to me. Now, if there were hundreds of reports of this across the country and around the world, the phenomenon would move from your first case to your second case. There would have to be a reason as to why all of the participants pictured a lizard person in their minds after they heard the sound. What would that reason be? Would it be an example of cellular memory, assuming that our ancestors dealt with such an entity in the forgotten mists of history? Would it be an example of a less popular Jungian archetype based on our shared dread of a reptilian from our collective unconscious, *or* would it be *your* example of an undefined entity projecting disinformation to hide the truth of what it is? Pardon my lame story, which just popped in my head.