Ride a horse in a multiplayer server (with a saddle). Log off while still on the horse. Log back in and there will be 2 horses in the same location (inside each other)(see screenshot). This happens in both survival and creative. I have not tested this in any earlier versions. This doesn't happen in single player.
29th duplicate of MC-13737, please use the search function to see if your bug has already been submitted. Currently over 56% of tickets are being closed as duplicate.