The North American Porcupine (Erithizon dorsatum) is the third largest rodent in the world, with only the Beaver and Capibara being larger. Common in Alaska, Canada and the coniferous forests of the Northern United States, they are rather slow and docile....but with a very effective defense against predators. They are covered with sharp, hollow quills, which are barbed and easily attach to an attacker...and are very difficult to remove.
Although slow moving and very nearsighted, the Porcupine has an incredible memory for it's favorite food source trees.
Here's a close-up of the quills. Folks in the "North Woods" who let their dogs run loose always risk a hefty vet bill to get them removed from the pooch's snout!!!