Cats are always grooming themselves so they rarely develop a nasty odor. You should pay attention if you notice a smell from your cat. Usually this is a sign that something is wrong. One of the most common odors is a fishy, musty smell that is produced from the cats anal gland. The oily contents of these glands are often released when a cat is excited or frightened.  Sometimes the glands become clogged and need to be cleared out by a veterinarian. The foul smell may stay on the cats coat for a few days.  If the problem persists, ask your vet to give your cat a thorough exam. Infections ,abscesses or impactions can result from chronic anal gland problems. So before you bring on the pet odor removal products have the problem checked out.