I have a cat who seems to find it more comfortable to poo while perched on the edges/corner of the litter box. Thus, the poop falls right outside of it (rather than in it). It drives me up the wall...it smells AWFUL! - but I'm not sure there's anything I can do about it. If I get a box with a lid, she poops out the door. I think it's her way of keeping her fur clean (she has remarkably long back leg,tail, and butt fur).