Dog-tired. Cat nap. Early bird. What do these expressions have in common?We say we're "dog-tired" when we’re simply exhausted. And cat naps might be the answer to make up lost sleep. With a good night's rest, you might even become an early bird. But if your pet actually is a dog, or a cat, or even a bird, restful sleep can be hard to come by. Because these pets can make it hard for you to "sleep tight" each night.