Getter Emperor is a massive, ever-expanding Getter Machine existing in the far future. It represents the unstoppableness of Getter Rays and becomes a threat to all life in the universe as a result of its sheer size and fire power. In all appearances of Shin Getter Robo, the Emperor has been alluded to; usually in the form of either the appearance of the Emperor's equivalent of the Eagle Machine or the machine 'evolving' in the case of Shin Getter Robo vs Neo Getter Robo. It has yet to have made a full anime appearance, though it has had cameos in both Getter Robo Armageddon and New Getter Robo.
Getter Emperor also made an appearance in Getter Robo Anthology~Will of Evolution~. He appears in chapter 1, 2, 4, 5, and 6. In chapter 1 he appear in a vision during a battle between a new Mecha Saurus and the original Getter team.  In chapter 2 the Āḥ team from Getter Robo Āḥ while battling a unknown Getter Robo also saw Getter Emperor.