Every time I think about leaving a dog in the car, I remember the time I left my Lhasa Apso loose in the car while I checked out of the hotel (goldens were crated in back).
It was a cold morning and he has unusually thin hair, so he was wearing a little doggy jog suit. While I was checking out, I kept hearing a car horn honking over and over. I looked outside to see what the problem was, and was surprised to see several people outside laughing and pointing. My dog was standing in the drivers seat with his front paws on the steering wheel. Every time he barked at the people outside of the car, the weight of him leaning forward made the horn go off. Everyone thought it was hilarious to see a dog in a jog suit with his hands on the steering wheel, honking at everyone who walked by!