Goofy is an anthropomorfized dog, but the demotion of Pluto is seen by many as Goofy.
Although Pluto is a pet owned by an anthropomorfized mouse - Mickey - but Goofy is independent and is seen as a person with all rights a person would have.
People's affection for the underdog (in this case undermouse) has always been in humanity, since at least David and Goliath, so Mickey has as an arch-nemesis an anthropomorfized cat, Pete (aka Black Pete or Peg-Leg Pete). Cats are selfish bastards and no one loves them, except for braindead lolcat lovers, which are mind controlled anyway. Pete is also older than Mickey by some 3 years and started out as a bear (that's a fact). It is unknown whether there was a gender change along with the species change it has undergone.
There is much controversy also about Donald Duck: first one is that it is not a duck but a teal, due to its gait and perched up tail. Also there is debate on the true origin of its 'nephews': the mother is (are?) never known, and it is speculated that Donald the Teal, in his life as a sailor, actually murdered prostitutes which fathered his illegitimate sons, and he adopted them out of guilt. He does not murder Daisy because she reminds him of his mother. Other theory is that it is actually Donald the Bear, the brown one with a friendly smile, usually seen around small kids, with perverse intentions.
So yes, there are countless rumors and controversy around Pluto, Goofy and the other celestial bodies in their vicinity in Disney planetary system.