So far their stock isn't the greatest on the planet, and it looks like they are womens only, but once something hits this point, piles of other merch tends to follow.
I know "knowyourmeme" announced this craze as a subculture a while back, but seeing it pop up at a store like this next to Zelda and Mario is a pretty big testament. They might not have the best reputation on the planet, but at least it does signify the inevitable pony takeover of...everything!
Links to the shirts are in the images!
Thanks to Lady Chu for the heads up!