Dogs and mirrors (or shiny windows)
Does your dog notice their own reflection in mirrors or window glass?
I had one dog who was so excited the first time he saw himself reflected in a shop window while walking downtown. Then he realized it was just himself and he was so disappointed.
When we first adopted our current dog he'd bark at literally his own shadow when he'd go out to pee at night, or at his reflection in the glass door. He quit doing that and when I've walked him up to a full length mirror, he just doesn't care one bit.