I found a huge egg in a tree hole next to our house it almost looks fake. I don't know if it could be an animal egg or someone put it there as a joke - but I wanna know how big can eggs get that animals lay?

I'm going to say the biggest egg an animal can lay would be an ostrich egg. Look up how large an ostrich egg is. If it is bigger or smaller than the egg you have, bring it to a veterinarian or some kind of animal research center.