Domestic cats can purr while they are breathing in and out, while big cats like lions and tigers can only purr when they are breathing out. Thus the sound is not continuous.
Domestic cats can't roar because the bones that support the larynx are rigid rather than made of cartilage like lions or tigers.
Non-spayed female cats can have a litter every four months. Each litter can have three to seven kittens.
A cat's brain is more similar to a human's brain than a dog's brain.
Cats can't see directly under their nose. That is why you have to point out the treats or tidbits they can't seem to find.
Cat's urine glows under a black light.
Ailurophobia is the fear of cats. Julius Caesar, Henry II, Charles XI, and Napoleon all suffered from this and would nearly faint in the presence of a cat.
Cats have scent glands in their face (also at the base of the tail). When they rub their face on you, they are marking you as theirs.
Chocolate is toxic to cats. As little as as few ounces can kill a cat. The darker the chocolate, the more dangerous it is.
Cats have a nictating membrane, which is an opaque inner eyelid. When a cat is ill, the inner eyelid partially closes sometimes, making it visible to the owner.
Calico cats are almost always female. If they are male, then they are sterile.
If your cat is in the habit of rolling over and exposing his stomach, you can be sure he feels perfectly safe with you. It's also a way of demonstrating his pleasure in your company