http://bloximages.newyork1.vip.townnews.com/postbulletin.com/content/tncms/assets/v3/editorial/0/bd/0bd57f60-7795-5f71-8ed4-87e6320b1e21/51fa8472ba87b.image.jpg
I see it around the internet all the time. I've even seen it in a manga scan once. But where the heck did it come from? What made it get such internet fame?

I think it originally came from 2ch and that you could order them from Archie Mcphee, but I don't know why there were worn so widespread. Probably because it's just an amazing mask to wear.

Its recent popularity on the western web puzzles me even more. One year ago it started popping up more on english websites and it's almost considered mainstream internet culture now. This sudden increase in popularity can't really be traced back to one viral video or picture; it's just generally becoming more popular.

In conclusion: the horse mask is just an amazing piece of attire that inspires anyone who happens to catch a glimpse of it. It's great that it gets more attention, but I silently mourn the loss of something that was iconic for only japanese websites; the mask has offically become 'un-cool'.

I think it became a "thing" on SA a long time ago and then spread to other western websites from there

I always thought it got popularized by this guy:
https://www.youtube.com/watch?v=ffDPTKn7HiY

https://www.youtube.com/watch?v=PxZ1NcG4W74

and he had other videos of him just doing plain weird shit in it