The name blue heeler (used for an ACD) comes from the "blue merle" colouring, which is actually mottled grey, white and black. I found an abandoned Lousiana Catahoula Leopard Dog (state dog of Louisiana) while camping on the coast of Louisiana and the vets and everyone down there thought it was a blue heeler or else a blue heeler mixed with a Cathoula. However, I did research and found out it was most likely just Catahoula, who also often have the blue merle gene. So other breeds can have the blue merle gene and are often mistaken as blue heelers. Mine looks a lot like the dogs in the movie except ears flop down halfway instead of straight up and she's less stocky, and is a tad taller and slimmer. Of those who guess, about 1/3 of the people up here in Canada think she's a Catahoula, the rest an Australian Cattle dog (blue heeler.) Both breeds can be rather aggressive, ACDs because they have terrier in them and are bred to nip at kicking cattle's hoofs, Catahoula's as they have been viciously culled by the Cajun's to breed the most aggressive and efficient hunting dog (originally partly from southern red wolf).