Squirrel? Hah!
I suspect that was not an Eastern Gray Squirrel. It was, rather, a Potemkin Squirrel, otherwise known as a lab rat. Strictly an invention of AA PR.
AA is not comfortable with the public knowing there are rats on board, even such aggreeable little critters as lab rats. Some of our airplanes have them living aboard. They escape from shipments. In the lower galley of 747s, I would look in the mirror over the sink and see one looking at me now and then. I have heard them at night on a quiet airplane, and have found one who died while chewing on the wire I was tracing. Lots of wires are chewed by them. I found a screwdriver with a rubber grip that had been chewed all the way around by a small rodent.
There are also regular rats in our hangar and around the terminal. The company sets out traps in both areas, but to little effect, it appears. In our tool box room, we use our own money to buy sticky pads to keep them under control. Since airport security has make me afraid to bring in a pellet gun any more, I use an air hose blow gun with a long tube barrel to launch a small screw at them. Not accurate, but sometimes I get one.
As far as cats, I have never heard one, but I have heard reports of someone hearing a cat meowing inside a darkened quiet airplane.