One time, when I was home alone, I was playing with my cat Maverick (named after the dude from TOP GUN), and he went out onto the little ledge on the outside of each stair (he had to be on the top one!) When I tried to coax him out,he tried to turn around and he slipped and fell. I could not find him for the rest of the day. The next morning, I found him and he was fine.