Playing possum

From Freepedia

Playing possum is a phrase that means to pretend to be dead.

It comes from a characteristic of the Virginia opossum, which is famous for pretending to be dead when threatened. This natural instinct does not always pay off in the modern world: for example, opossums scavenging roadkill may use it in response to the threat of approaching traffic, and end up as roadkill themselves.

References

• Ways to avoid hitting animals with cars.