Hi! Every kitty has his own personality so different cats may show it in different ways. I was chosen by Groucho when he was 7 weeks old, he was 4 in March. The signs I see that he's happy are that he's very friendly and doesn't run away when someone comes over, he goes right to them and wants to be friends. When he walks around his tail is always straight up, he purrs a lot and is very affectionate (when he wants to be). But I guess the most obvious sign is the way he'll roll over onto his back demanding a tummy rub. I've heard that this is the ultimate trust since their underside is the most vulnerable. He greets me at the door every day when I come home from work most often on his back waiting for his hello tummy rub. In the morning he stays right by me as I get ready for work. When it's time to leave, Groucho is right by the door meowing and asking for one more tummy rub before I leave. There was this one morning when my backpack seemed a bit heavier than usual. Opened it up and there was Groucho inside. Guess he wanted to spend the day with me at the office. Groucho has a very sweet personality and is extremely friendly to everyone. He gets lots of love, affection, and care. Our vet once said this is because he knows how much he's loved and is responding to it. I don't doubt that he's a very happy kitty.....