While, possums are perhaps the most notorious for putting on a lifeless air in response to the slightest sense of danger, this defense mechanism has been observed in insects, birds, reptiles and a variety of other "prey" mammals, including rodents.
Some skittish pets, like hamsters, have retained this survival instinct to freeze up like a corpse, even when facing down the barrel of a "finger gun." In other words, the adorable little animals in the clip above are probably not happily playing along with their owners like furry little actors, they're more likely frightened by the sound of the "bang."
http://www.youtube.com/watch?v=7nhll1UslDg And while it may be quite cute to watch, those in the know say that eliciting this behavior for fun is a bad idea. Not surprisingly, being scared too often can cause stress and anxiety-related diseases and even death -- one they won't be faking.