Sometimes the best way to deal with winter is to just say "forget it" and sleep through it. That's what many of our animal friends do when the weather gets too cold and food becomes scarce, but which animals actually hibernate? Some animals go into true hibernation: their heart rates and metabolisms slow down, and they pretty much don't wake up until spring. Other animals go into something called "torpor," or a light hibernation, and might sleep for days or weeks at a time, but they get up occasionally if disturbed or if they want a midnight snack. One animal even freezes, develops ice crystals in its blood and appears dead, but still thaws out in the spring like nothing happened.Scroll through this list of the animal world's champion sleepers and find out which critters have woken up from a long winter's nap. The next time you feel guilty about sleeping in, rest easy knowing that you have nothing on these guys.