It is known as مازنجر الكبير ضد جيتاروبو in Arabic countries, Grande Mazinga contro Getta Robot G in Italy and Gran Mazinger contra Getter Robo in Spain.

Later, despite the robot pilots' protests, their two bases decide to join forces to stop Gilgilgan as he starts becoming more powerful and begins to change.

The combined heroes almost defeat Gilgilgan until the UFO returns and allows itself to be eaten to cause its own creation to grow to its final form.

The primary antagonist of the movie, Gilgilgan is a tortoise-like bioweapon from outer space used to conquer Japan primarily by living on a diet of nothing but metal and slowly grows larger into two other forms.

Once it eats its creator Gilgilgan will change into its third form which appears more like a demon where it can fly and its powers include finger lasers, bladed wings that can also fire energy beams, and has three whip-like tails.