SCP Foundation

Next you need to decide on how it's discovered, based on the description it actually vaguely reminds me of a short joke on The Simpsons where marge fed her new mop, some scraps. Perhaps the mop belonged to an as yet unknown anomalous cleaning company that uses anomalous tools to perform their tasks. They keep these mops, which act a lot like sniffer dogs, snuffling along, soaking up dirt and dust. And wring out the waste as dirty water. I think an ever-present smell of fresh pine should hang around it. Story-wise it was initially mistaken for one of those shaggy dogs, it got trapped in one of the buildings the cleaning company visited and after it's whining/cries for help were heard, it was rescued, and taken to a local animal shelter. Given its friendliness and usefulness in cleaning up dirt/food scraps, dog pee. The owners kept it in secret, until the Foundation discover it, while tracking down another anomalous animal. Investigation into the company is still ongoing, trying to track down and confiscate their cleaning buddies. I like to imagine the cleaners are like these extra-dimensional beings that come into our reality to work. And are able to teleport back home, hence why capture has been so hard.

Based on its friendly nature, tests should be more to determine what it can and won't eat. Maybe a behavioural study and things it likes to do, like play fetch, go for walkies, chase insects or clean etc.