I believe. somewhat. was playing on the 360 version and was watching some vids about summoning herobrine and how to do so, pne vid showed how (3x3 grid of gold blocks with moss stone in the middle, netherrack on top of the moss stone, 4 Redstone torches in a diamond shaped pattern on top of the gold and surrounding the netherrack, then light the netherrack on fire with the flint and steel and stand still) and another showed a few things that had happened to them, like different animals jumping on top of the herobrine alter and staying in the fire long enough to die. I had already created my alter and was holding position while finishing the second vid, saw a few animals die by fire (on the vid), and when I finally looked up at the tv screen, a pig had got on top of the alter and was looking at me while it died in the fire. I don't know if it has something to do with herobrine, or the alter has some weird magic to it that draws the passive mobs to their deaths. well, like I said, was on 360 version. I never saw him/her/it, but I wasn't looking at the screen the whole time either, so yea.