The opossum is the only marsupial (has a pouch like a kangaroo) native to North America. They rarely cause any problems for homeowners. They may dig under a deck, shed, etc. but unless they die in their den they will not cause any problem except cosmetic ones. They always carry their young with them. They are omniverous in their feeding habits and will visit bird feeders as well as knock over an occassional garbage pail. They are good climbers and are very comfortable in trees because of their prehensile tails, although I have never found them in attics.
"Mom" possum with her young on her back