I'm seeing some people talk about Mega Raichu X and Y and there are many comments comparing them to the unreleased Gorochu… and I'm almost certain they're confusing leaked content with fanart.
I'm not saying that people making this comparison is wrong, though, I think that the original idea might have been used as an inspiration for the new megas.
And before you doubt that it ever existed in the first place: Gorochu was originally revealed in an official interview in which its original designer, Atsuko Nishida, reveals its name and a small description: "Its name was Gorochu. It had fangs and horns and looked like a god of thunder.” So it kinda fits with one of the most popular fanarts.
And to be clear: This leaked sprite isn't actually confirmed either, but it's most likely real… a front art should've existed too, but the leakers apparently didn't get it.
by Tydram