After I tipped the can over, the opossum refuses to leave. Apparently, the whole "playing possum" thing is genuine -- according to Possum Rescue, they will respond to any unusual situation by performing the death scene from Citizen Kane with added drooling. If that doesn't work, they can fake a coma:
When unable to flee, extreme fear places the opossum into an involuntary coma. They become stiff and their mouths will gape open. This condition will last 40 minutes to 4 hours. Most predators will abandon their attack, once the opossum is thought to be dead.
I'm going to try this the next time I find myself in an uncomfortable social situation.
I'm a watcher of possums also.
I wouldn't count on a possum playing possum. I've heard they will attack viciously, when they open their mouth look at those choppers. The critter you mentioned was trapped but they are nocturnal scavengers, if you see one in daytime it is either spooked and fleeing something or it may have rabies. They should run from you, if not they could be ill and looking for a friend to BITE!
Any cornered animal might bite, but everything I've seen indicates that opossums are much more likely to die from fright than to attack. An animal rescue volunteer came to my house after the opossum refused to leave the can. She grabbed him by the tail and put him in an animal carrier with no trouble, and he sat meekly at the back with his mouth agape in the least-convincing snarl I've ever seen. Also, unlike a lot of other animals, opossums are extremely unlikely to carry rabies.
None of this means I would be willing to grab one, of course.