The Hat Man. I saw the tumblr meme a few years ago (already a few years after it was made). It's funny. Telling Mary about it, I did a quick online search.
Our #culture apparently can't leave anything alone. Maybe, with the death of the monoculture, we're all desperate for some shared references. Maybe some Very Online People have made little micro-cultural groups that spread through larger cultures like mycelia.
There is now a little subgenre of Hat Man merch (t-shirts, etc.) and at least one low-budget horror movie titled The Hat Man, so #capitalism had to get its hand in, too.
This makes me simultaneously more and less interested in The Hat Man as a phenomenon.