I have six cats. Can't tell you if they actually "smile", but I can tell you when they are content, they will be purring and sometimes butt their head into you like a battering ram. May have their eyes halfway squinted and ears facing forward. One of my guys will rub his body along my leg and then just flop over in the floor and look up at me and meow, like he's saying, "So, pet me already! Give me some love!" I'd say that is better than a smile. IF cats can smile...don't know....
I also have six cats, I believe they do smile. If you look at them from the side you can see the smile if they are happy. It is funny because I always thought if a cat wagged their tail they were mad but all of mine do it when they are happy!!! Believe me you will know if your cat is not happy, they are very smart, they will let you know!!! Remember the saying Dogs have owners, cats have staff???? It is true!! If our alarm clock doesn't go off in the morning they will wake us up, right on time also!! Unfortunately the do not know the days of the week and don't understand weekends are for sleeping in. You can also train you kitty!! We have Tinker who fetches, LuLu is the alarm, Gabrielle sits pretty, Angel has a turtle dish and when you tell her to go to it she will, Timmie will tell you if someone isn't a good character, Cassidy catches spiders(big ones too!), They all sit and wait their turn for treats and they will sit, lay, sit pretty or whatever I ask them, too bad they don't clean the house. But they are self-cleaning!!!!!
