Black Hole Aliens
The Black Hole Aliens or "Simeons" are a race of extraterrestrials hailing from the Third Planet of the Black Hole. They are all green humanoid apes, and although they can disguise themselves as ordinary humans they revert to their true form upon death or injury. Because their homeworld was disappearing into a black hole(Possiby Gorath), the aliens sought to conquer and colonize Earth using their robot, Mechagodzilla. Both times they were stopped by Godzilla.
Fans have designated them the "Simeons," based on their appearance.