There was a film out donkey's years ago called Zoltan, Hound Of Dracula. It featured a very weird looking Italian actor whose main claim to stardom (in Italy, at least) seemed to be he was...weird looking, as I don't think he spoke any lines throughout. He played the dog's handler, and he mainly stood in the background looking ominous.
Zoltan couldn't have been a sheepdog by day, of course, because he would simply have fizzled to a skellington. Imagine that on One Man And His Dog, a whistle, some bleats, a bark, the sound of frying, and sheep running loose all over the Cotswolds.