If the alleles for leopard and pied fell on the same locus, it would be impossible to get leopard pieds. It is more likely that they are located in close proximity on the same chromosome if in fact the "all leopards are het pied" bit has some semblance of truth to it. However, I think this idea people have may only be due to the fact that leopard was tied into the pied project by Pete Kahl from the get-go. I would expect to start finding that the leopards that being produced from crossing the mutation into others aren't all het pied.