Leapin' Crickets.
In the hallway in my house, something black started jumping around on the ground. I turned on the light. It was a cricket, and it looked like this:
I caught it with a transparent cup and a paper plate. I walked it outside and released the cup from the plate. It hopped into the grass.
I'm glad it wasn't a miniature hydra.
That might mean that it is time to thoroughly clean the house.