Bubba the Wonder Doof for years would get quite perturbed when he jumped up on the bathroom sink and saw That Cat in the mirror. He didn’t try to attack it but he’d meowl relentlessly in his gravelly bitching voice until I’d come, remove him from the bathroom, and shut the door.
When he was about 5, I moved. When I let him out of his carrier, he went all over the apartment inspecting everything. All was well till he got to the bathroom, jumped up on the sink, and saw…That Cat had followed him!
To make matters worse, the new bathroom had both a mirror over the sink and a mirrored medicine cabinet at a right angle to the big mirror. When he raised up on his hind legs to inspect this Fresh Hell, not only did That Cat mimic him but now there were multiple versions of That Cat. Oh, there was torment…
A little later, I got a second cat. This put Bubba’s nose out of joint but he never fussed about That Cat In The Mirror once another real cat was in the house. I think he decided That Cat at least knew his place and, outside of the mimic thing, had the decency to leave him alone, unlike that Upstart Kid Cat that moved in.