I have an outdoor fenced in area so my cats can go outside when they care to. One night, I knew that two of my cats were outside, but saw three bodies in the enclosure. Flipping on the floodlight, I saw two cats and an opossum within the chain link fence! Fearing that their curiosity towards the intruder might lead to violence, I had to get my cats in quickly, so settled for a hand-held spotlight with which I blinded and held the opossum at bay until I could corral the cats and bring them inside. Somehow the unwanted wildlife had squeezed in around my yard gate or perhaps climbed the fence, and I was grateful to have found a non-violent solution to the intrusion...
When I was in Texas, there was a possum outside with our cats and they were ignoring the possum completely. A common reaction among cats to an animal that they don't see as prey or as a danger is to pretend that it doesn't exist. I've seen Ella do that with skunks and with a groundhog that was in the process of digging a hole. I thought Ella would be interested in the groundhog since it was right there, digging. Instead, Ella acted like she couldn't see it.
We had a family of 'possums in our attic in the first house we lived in in Florida. I swear those things were wearing Army boots.