All rodents have a pair of upper and a pair of lower teeth called incisors. Unlike our teeth, these incisors don't have roots, and they never stop growing! If they didn't gnaw constantly to wear them down, these teeth would grow until they pierced the opposite jaw.

A group of alligators is called a congregation. A group of newly hatched alligators, or juveniles, is referred to as a pod.

Nine-banded armadillos always give birth to identical young formed from the splitting of a single fertilized egg. Among mammals, this is unique to nine-banded and other Dasypus armadillos.

In the United States and Canada, the only species found is the Virginia opossum, and it is generally referred to as a "possum".