Beware of cat on window air-conditioners
a) Take them in during the Winter. However short the winters might be, a window AC unit is a sieve.
b) Purchase a unit that does not have slats on a horizontal surface. Most do not.
c) We put a soft fleece cover on our AC units (when they are in). Secured with Velcro. Easy to install, easy to remove and easy to keep clean.