An unwelcome pet.
A stray that wanders in and has been eaten all the birds in the garden before you even know it's there. Before you really see it, you are feeding that stray and it thinks your house is it's house.
It finds it's way inside, it wants to sleep on your bed.
Then you have to call a beast wrangler to drag the fucker out of your building. Given the general availability of beast wranglers, and the paperwork involved, the mongrel thing has probably pooed on your couch and chewed up your best dress before the expert arrives. It's evicted with a great howling and shedding of blood. Body parts are lost.
Of course, its a protected species which you can discourage, but can only kill at risk of your own life.
So, the bloody thing is now outside, looking in the back door, licking at the glass. It wants to come back in. Even if you pull the curtains so you can't see its beady little eyes staring at you, you know it's still out here.
My unwelcome pet. Mxx