First time I got stepped on I was about nine and taking this bratty draft mutt out of his stall to tack him up. About 3/4 of the way out he decided working wasn't on his list of things to do and he very carefully turned around, stepping directly on my foot, and returned to his stall. I was quite upset with him for sometime and lost my baby toe-nail from it, but, once I got a baind-aid, rode him to prove a point.
My current horse occasionally insists that I scratch his rump, and will back up into me until I notice him and has occasionally stepped on my foot. He apologizes profusely. :)