Could they climb certain kinds of exteriors? Maybe some of them were in the trees or on the roof like a creature feature and the caller didn't realize it because it's night.
Or maybe they're actually hover cats. lol Didn't the police find some weird collar on them? It could have powers like the collar on the cat from outer space?
I assume we've all wondered whether the cats are "real" in various different applications of the term, illusions, AI, etc. Space cats? lol
This is veering off the subject but now that I've thought about space cats, and researched the term because I couldn't remember the name of the movie, I feel I have to share this hilarious bunnies in space video because, well, everyone needs to see it -
https://www.youtube.com/watch?v=Punzp4ektVM