Well, Cochise is an aussie.
So far I have heard "mixed with what???, Aussie's are only black and white" That was about my favorite so far.
I have also heard dalmatian, catahoula leopard dog, sheltie (he's already too big for that), husky, and border collie.
I have to say that I wish if people didn't know what he was they would just politely guess rather than make silly comments such as the one up above, or "Aussie's don't come in that color" or "well he's a funny looking Aussie."