Hopefully you will forgive the long description... but there are so many interesting and unusual things about sloths.
They are named after the capital sin of sloth because they seem slow and lazy at first glance; however, their usual idleness is due to metabolic adaptations for conserving energy. Sloths move only when necessary and even then, very slowly; they have about a quarter as much muscle tissue as other animals of similar weight. They can move at a marginally higher speed if they are in immediate danger from a predator (up to 13 feet per minute), but they burn large amounts of energy doing so.

Other notable traits of sloths include their strong body and their ability to host symbiotic algae on their fur. Because of the algae, sloth fur is a small ecosystem of its own, hosting many species of non-parasitic insects. Sloth fur exhibits specialized functions: the outer hairs grow in a direction opposite from that of other mammals. In most mammals, hairs grow toward the extremities, but because sloths spend so much time with their legs above their bodies, their hairs grow away from the extremities to provide protection from the elements while the sloth hangs upside down. Their specialized hands and feet have long, curved claws to allow them to hang upside down from branches without effort. While they sometimes sit on top of branches, they usually eat, sleep, and even give birth hanging from limbs. They are classified in the same family as anteaters, which sport a similar set of specialized claws.

They have large, specialized, slow-acting stomachs with multiple compartments in which symbiotic bacteria break down the tough leaves. Sloths' tongues have the unique ability to protrude from their mouths 10 to 12 inches (25 to 30 cm), an ability that is useful for collecting leaves just out of reach. As much as two-thirds of a well-fed sloth's body weight consists of the contents of its stomach, and the digestive process can take a month or more to complete.