Pheebie gets freaked out by plastic of any kind if it is making sound like blowing in the wind or being scunched up after going to the store. Once we were outside of Kohl's and a lady walked out with these huge pillows covered in clear plastic. It was a windy day so the plastic was rustling. Pheebie lost her mind! Another time an empty plastic bag fell on the driveway and the wind picked it up. She barked like it was an intruder.
I like to think maybe she's just senstitive about the environment and is protesting plastic bags in general.