Playing dead is an involuntary response on the part of the opossum. The stress of the confrontation facing the opossum causes him to go into shock.

Do possums like to play dead?

Opossums don't actually play dead when they're threatened. Instead, they involuntarily enter a catatonic state. ... Many people believe it's a good act, but according to scientists the possum is actually in tonic immobility or thanatosis, and its body enters a catatonic state in response to fear.

How can you tell if a possum is playing dead?

Commonly after an hour, the ears of the Opossum start to move slightly. This is your indicator to know that it's an actor :) After four hours of stiff ears, you can be pretty sure that you are looking down on a dead animal. Call the competent authority (local veterinarian, wildlife rehabilitator, animal control etc.)