Replying to Mystery animals in your house

This afternoon I was hanging out, watching TV in my basement suite and I looked over and there was a cat sitting on my table. I didn't have any windows or doors open and had been in my place for a few hours. I didn't run out or leave any doors open, yet somehow there was a black cat just sitting there, staring at me. I just about had a heart attack.

Has anyone else had random animals mysteriously show up in their place?