I was reading an article in G-Fan about the various alien species in the showa series. One part brought up an idea or two as to why the Black Hole aliens appeared as apes in GvsMG, but rather disfigured human beings in ToMG. The author wondered if perhaps there were two seperate species living on the Third Planet. His other thought was that their monkey ape forms were faux disguises so as not to reveal their deformities.
I disagree with both of these ideas.
Considering the hostility of the Black Hole aliens, I seriously doubt two seperate species could peacefully coexist on their home planet.
As for the idea of a gorilla disguise...if they had the ability to choose what form they took at death, why wouldn't they just opt to stay as humans?
One explanation I've come up with is that the aliens tired of regressing to their ape forms when wounded or in distress. As is obvious by the chase sequence on the ship in GvsMG, the half-ape alien had a difficult maneuvering and lost the ability to speak. Perhaps the ape form forces limitations on the aliens.
That is why I think the aliens may have attempted to perfect a means of becoming human permanantly. However, it's evident that their attempts failed with horrid results, such as disfigurement.
Just an idea...
Anyone else have any explanations?