We have a stray cat using our cat door, eating off of our counter tops and all of the food in our cat bowls. Has anyone else experienced this? What do we do to stop it? We can't necessarily leave the bowls empty.
There are cat doors you can buy where your cats wear a special collar, and it only lets in your cats, not stray cats. I would say put a chair or something in front of the cat door for now so that your cats can't get out for a little while, and the visitor can't get in. Try looking online for those cat doors with the special collars--it might be worth switching the door to one of those.