Baby opossums are born 13 days after conception - the shortest gestation period for any North American mammal. At birth, the young have the size, shape, and appearance of embryos, yet crawl across the mother's fur and into her pouch where they will nurse more or less continuously for the next two months. The mother's pouch protects the young and keeps them warm during this period. Average litter size is 8 or 9 young. Other hotbeds of opossum folklore concern its habit of playing dead and the use of its prehensile tail.
Opossums do play dead.
When faced with danger, opossums sometimes run away, sometimes bare their teeth and hiss, and sometimes fall into a catatonic state in which they appear to be dead. This behavior has been associated most closely with opossums because they are relatively large, relatively common, and because they are so good at it. Opossums play dead for periods of several minutes to several hours at a time. While playing dead they do not respond if they are poked, their whiskers are pulled, or even if their eyes are touched. Apparently playing dead is an involuntary response which confers some survival value on the participant.