I had two cats, brothers, Moxie and Pepsi, who played together constantly.
I know I am anthropomophising here but, Moxie was, in my opinion, somewhat mentally challenged. Most of the time he did not act like he was all there and his reflexes were slower than most other cats I have known. Also, he could not meow properly. It came out as an eh..eh….eh. sound. He was, however, deeply affectionate.
In addition to playing together, Pepsi seemed to watch out for, his brother; making sure he made it home safely in the evenings. At dark he would come inside and prowl around looking for Moxie. If he didn’t find him he would go to the door and mmmmmmmowl until I let him back out. Usually within 30 minutes he was at the door asking to be let back in and ALWAYS had his brother with him. He would stand at the food bowls and “call” until Moxie would come over and then sit back and watch him eat. Once he had his fill, Pepsi would then take his turn at the bowls.
They were good cats. I had them for about 9 years. One day Moxie did not come home. Pepsi seemed to be extremely upset. He would not eat much and spent an inordinant amount of time gone from the house and yard. Two days later, Pepsi did not come home.