From wikipedia.com:
Opossums are typically 15–20 inches long and weigh between 9 and 13 pounds. Their coats are a dull grayish brown, other than on their faces, which are white. Opossums have long, hairless, prehensile tails, which can be used to grab branches and carry small objects. They also have hairless ears and a long, flat nose. Opossums have 50 teeth (the most among land mammals) and opposable, clawless thumbs on their rear limbs. The Virginia Opossum is noted for its reaction to threat, which is to feign death. This is the genesis of the term "playing (o)possum", which is used to describe an attempt to pretend to be dead or injured with intent to deceive. In the case of the opossum, the reaction seems to be quite non-voluntary, and to be triggered by extreme fear. It should not be taken as an indication of docility, for under serious threat, an opossum will respond ferociously, hissing, screeching, and showing its teeth. But with enough stimulation, the opossum will enter a near coma, which can last up to four hours. It lies on its side, mouth and eyes open, tongue hanging out, with green fluid emitting from its anus, and emitting an odor putrid to most predators. As a result of this unusual behavior, opossums that are discovered apparently dead with no obvious fatal injuries should be given the benefit of the doubt as to avoid inadvertently burying them alive. Though some humans are fond of these creatures, many consider them to be rather ugly. They are commonly encountered as road kill. Like raccoons, opposums can be found in urban environments, where they eat pet food, rotten fruit, and various human garbage. Housecats have been widely reported to be surprisingly tolerant of oppossums. Some opossum lovers claim that they provide a valuable service to humans by competing with and eating other, more disease-ridden vermin. The Virginia Opossum is the original animal named "opossum". The word comes from Algonquian wapathemwa, not Greek or Latin, so the plural is opossums. Colloquially, the Virginia opossum is frequently called simply possum.

On a more personal note:
Although I have never had or even held or touched a live possum, I do have a wonderful stuffed possum named Max. He's not camera-shy [in fact, quite the opposite!] and likes to travel, drink beer, and irritate the cats. He especially likes to dance to the "Curb Your Enthusiasm" music!