I'm willing to bet you that you've never seen that man in any of your dreams, ever.
The human mind is incredibly suggestible thing, one could relatively easily convince most people that things happened to them that, well, never happened.
I'm sure that you're aware of the "repressed memory" controversy that happened several years ago? The one with the people who became convinced that their parents were satan worshippers, and that they had been raped and molested as babies? You're aware that every single one of these so called "repressed memories" was complete and absolute bullshit? That the people actually began forming flase memories simply because they were being asked about the situation, and their brain made shit up?
Other experiments run have had similar results, where psychologists take people and then talk to them about their trips to other countries, except those people never actually went to any of the countries that the researchers told them they went to. They showed the subjects images where they were photoshopped into pictures of the country, and through conversation, they eventually convinced the subjects that they really had gone to the countries they never went to. The subjects even took the lead, making up stories about the time they spent there.
This is because people tend to forget about things, like, a lot. We forget an unholy amount of stuff all the time, so when we see evidence of us doing something, or people say we were doing something, then our brains will just assume they forgot about it.
So we already have an easily suggestible mind.
Now, let's look at dreams.
Vague, insubstantial, and most of them forgotten, with the ones you remember almost completely made up to fit the holes in the story formed by what you remember.
You're almost certainly never going to remember any kind of face from your dreams, other than some vague, human-like one.
So your easily suggestible brain, coupled with your vague, foggy dreams, will likely easily believe that THAT man was actually in one of your dreams, despite the fact that he never was.
Look at his face, it's vague, a face that someone will almost never see on a human. The mouth is too wide, it's in black and white, and it has no distinguishing features. Really, you can only see half of a real human face on that thing.
I'm thinking that one day, some kid had a dream, and there was a man in it. When he woke, he decided to draw the vague human-face that he remembered, and he got this.
Then, a friend met up with him, asked him what that was, and the kid answered "Oh, that's a guy I saw in a dream".
A while later, the friend "realizes" that he saw that man's face in HIS dream too. Except he didn't. Chances are, his dream never even had a man in it, and if it did, it was almost certainly not an identical copy to the paper one.
And thus, it spread.
And the problem is, after people convince themselves that the picture is a real man that they see in their dreams, they will actually start seeing that exact face in their dreams, because their minds have become convinced that when they dream, they will see this man, like everyone else.
It's a self-perpetuating falsehood.
I guarantee you, Ryan, that you have never dreamed of this man before you saw this paper. Though you might dream of him in the future, now that you've seen his face.