According to the Roomba FAQ over at McSweeney’s, these are the tell-tale signs: excessively long charging periods, vacuuming the same spot over and over, and not moving at all.

IF your Roomba starts drawing pentagrams in the carpet, vomiting, and climbing up the walls, you have a bigger problem on your hands. Sorry. Do not under any circumstances leave your Roomba home alone. Ever.

Credit: Roomba by Onur Binay