Thanks to walterflanagan for this. He says:
I have absolutely no background on this amazing mini pony other than all these pictures were posted in a LiveJournal baby animals community I am part of. According to the original post the person "Went to a petting zoo and there was an adorable baby miniature horse!"
I have no idea how livejournal works. Much like tumblr and a few other online entities. I'm a pretty badly-informed blogger. But any livejournal that has mini ponies obviously knows what's up.