I know this may sound weird but it 100% happened. I was standing at the GE waiting to buy some items and i saw a cow and either a player or an NPC ( I'm not 100% sure ) both spawn at the GE. Next thing i saw was the cow turn around and kick the player/NPC and they went flying and then both disappeared. The Player/NPC was wearing red/pinkish robes and the Cow was brown but not like others cows the one i saw was all brown with no patches of white like regular cows. It all happened so quick i didn't have time to hover over them, There was about 3 other players around but i tried asking if anyone else saw it but got no response i assumed they where bots. I've just recently came play to playing OSRS so i'm not sure if it's some teleport animation that i'm not aware off.
