Why does your cat chew on plastic bags?

This is a difficult behavior to explain, and some cats are more prone to it than others. Most feline behaviorists have come to believe that some cats find a slight odor to the plastic and/or photograph surfaces simply irresistible, and also that the coolness and texture of the plastic and/or film must feel and taste good on the cat's tongue. It may also be another form of trying to "nurse" - sort of a feline "oral compulsive" behavior. Completely harmless so long as they don't actually eat any of it. Although the constant russling sound is a little annoying for the cat owner.