Goofy Sex

Everybody knows who Donald Duck is, and by extension, his nephews, Huey, Dewey and Louie. I am not sure whether Donald is technically married to Daisy Duck, at least within the confines of the fictional Disney universe, nor am I sure how these ducklings are technically related (are they his sister's kids? Brother's?). I suppose it does not matter much, but what does matter to me is who sired Max, the dog I have been assured is Goofy's son. I am unaware of any female counterpart for Goofy. And I just can't picture Goofy humping another dog. Or maybe I just don't want to. And yet, the identity of Max's mother continues to elude me, much like viable topics for this blog.