Cats spawned by villagers are often missing their skin texture and don't despawn or approach you with fish in your hand. May be some kind of ghost cats, I have got these in my world for about 3-4 times in a row (just spawning by the village, not intentional breeding). They even dont take fall damage but can be killed by hitting or /kill

I play in 21w14a in an extended world, so I can't check it in newer snapshots or 1.16.