I'm not a geneticist, but as I recall the spider gene is a dominant gene, which would mean that only the spider offspring should or would have the wobble since it would be the only offspring that would have the spider genetics (normals would not carry any of the spider gene, hence no wobble). Other animals that have a wobble didn't get their wobble from a spider down the line in it's ancestry... IMO. I believe the wobble found in other animals is a random anomoly that just happens..... Like bug eyes, or duck bills, etc. I know that some of the things I named are linked to specific morphs, but it can also happen to normal or wild type offspring too.