O-Dear

Possum: an order of marsupials (Diprotodontia) native to Australasia.  Possums range in size from from that of a small-ish mouse to that of a large-ish cat.  Species can be omnivorous, herbivorous, insectivorous, and even specialist eucalyptus or nectar feeders.  They are nocturnal and mostly to entirely arboreal.  Some species have adjusted well to urban habitats, but others are threatened or endangered by human presence.

Opossum: an order of marsupials (Didelphimorphia) found in the Western hemisphere, most likely originating in South America, but which has spread up the Eastern coast of the USA and even further north than Toronto, as well as West through to Middle America.  Opossums range in size from that of a small-ish mouse to that of a large-ish cat.  They are omnivorous, have immunity or resistance to an unusually large variety of toxins and poisons, hold the record for toothiest land mammal, and sleep in the daytime.  They have been known to "play possum," but their semi-prehensile tail doesn't allow the mature adult to hang upside-down from trees (although young opossums have been known to dangle for brief spells).

If you're thinking of a possum, you're most likely actually thinking of an opossum.  Sorry.