have you ever seen one of these?

Great Pyrenees
I had not, but I met one named Mookie (I think I had an ewok with the same name).
Here is some info on the breed:
The Great Pyrenees, also known as Pyrenean Mountain Dog, is a very old breed, and has been used for millennia by the shepherds which includes Basque people, who inhabit parts of the region in and around the Pyrenees Mountains of southern France and northern Spain. More recently, the breed served as the official dog of the royal French court (whose prominence began circa the Middle Ages, and lasted until the middle of the nineteenth century). During World War II the dogs were used to haul artillery over the Pyrenean Mountain range to and from Spain and France. They are related to several other large white European livestock guardian dogs (LGD), including the Italian Maremma Sheepdog, Kuvasz (Hungary), Akbash Dog (Turkey) and Polish Tatra or Polski Owczarek Podhalański.