Occasionally I will see two, or even three, enemies running around the circuit in exactly the same spot, meaning they look like some multi-headed, multi-limbed creature.
I saw it on one of the roads in Mooshu, and I have a picture of a couple of cat burglers in the Isle of Dogs sewer:
(edit by One-Eyed Jack: Thanks for the picture. Deleted link.)
Not sure if this is a related bug, but I sometimes saw Tengu and Oni just standing in the road, not walking around. I saw this only in Mooshu, usually when there were monks wandering the streets, but in one location it was Oni.