I have a cat that’s about 20. She used to be an outdoor kitty, and fairly cranky, until she discovered that inside was nicer. Now she is stone deaf, and has alzheimer’s. She has forgotten that she was cranky and wants to be a people cat now.
We have a dog who is developing doggie dementia, we believe. Stares at a corner for long periods of time, stuff like that.
All the cats are still good.....they now treat him like a big mama cat and burrow in his fur.