The other day, I was in ice crown, doing some dailies. Inside a group of mobs, I saw horde symbol on one of the mobs, and saw it attacking the other mobs, which was strange. I proceeded to attack the mob, and suddenly it started running and hugging the mountain side. It then turned into a gryphon riding horde and flew up the mountain to safety. Unfortunately, I couldn't follow it cause I was in combat.
Another instance was a dead gnome npc, just floating by, pathing down a flight of stairs, going into a quest room like it was trying to quest.
I have seen similar things. Today i had a horde player i was attacking turning into a horde symble gryphon. I couldn't find the player again. It was strange.