Don't be fooled into thinking that Catz (or its sister title, Dogz) is actually a game. They're not. They're more along the lines of experiments into artificial life that ended up getting published under the guise of entertainment. That, or they're interactive screen savers.
In Catz, you control a disembodied hand and survey the cat of your choice as it scratches, eats, drinks, chases yarn, sleeps, and meows in a playpen. You can choose from lively calico cats, demure Siamese cats, and voracious Persian cats. With the interactive hand, you can pet your cat, brush it, feed it food and treats, spray it with a water bottle and do almost everything you can do to a real cat. The cats all have corresponding bars ranging from happiness and age to affection and grooming. If a particular area of a cat's upkeep is neglected, the cat will run away. The goal of the "game" is to raise a healthy, vibrant cat so it can be retired to the Catz hall of fame. You'd think the bars would be continually changing, making caring for your kitty a challenge. Unfortunately this is not the case, as the cats seem more than happy with the occasional brush, pat on the head, and ball of yarn. Yawn.
The only other feature this title has (and it's a small one) is one that lets you swap cats and special toys via an infrared link with other carts, letting you see how other Game Boy fans (mis)treat their cyber friends. This e-trading is clearly aimed at younger children in an attempt to spawn Pokemon-type addiction, but Catz just doesn't have the charm (or even a hint of gameplay) that makes its model so appealing.
There could be a case made that this game should have been called Sim Feline, but there's virtually no required interaction with your virtual pet. Kids with allergies or other prohibitive reasons might love this title, but anyone who calls himself a gamer will probably view this title as little more than a drain on battery power. To paraphrase Springfield anchor Kent Brockman: "I won't shed a tear if this little kitty is put to sleep."