Although domesticated felines don't have the same need to hunt as their wild counterparts, house cats are still physiologically hardwired to be active at night and sleepy during the day, which is why "catnaps" are no joke. The average cat can sleep up to 18 hours a day -- and kittens can often sleep longer. That doesn't mean curious newborn kitties don't want to play all the time; it just means they might play themselves to sleep, like the little cat in this video.