Poltergeist? Hermione shook her head and tried not to whine. "I - I don't think so. I've used that spell to clean the litter box ever since I got Crooks and it's always worked perfectly. This time, though - "
She gestured helplessly at the mess. "It exploded, right after the sand cleaned itself. I've been working all day and thought it was just me being tired, but I've never had anything like this happen before!"