Duke Fleed is a survivor of the Vega Star, raised by Dr. Umon as his adoptive son, and known as Daisuke Umon on Earth. Years after his arrival, he\'s faced with the threat of King Vega and his army, who want to conquer the Earth. With his friends Koji and Hikaru (and later his kid sister Maria Grace), Duke decides to fight back using his best weapon - the almighty Grendizer.

UFO Robo Gendizer was not released in North america. UFO Robo Gendizer is TV remake and continuation of the pilot Movie entitled Uchuu Enban Dai-Senso Which Premiered 7-21-1975.
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There was a spinoff Movie Grendizer - Getter Robo G - Great Mazinger Kessen! Daikaijuu in which A giant sea monster known as \"Dragonsaurus\" has emerged from out of nowhere, terrorizing the depths of the oceans. Great Mazinger, Grendizer and the Getter Robo G team join forces to combat the new threat. But their task becomes more complicated when Dragonsaurus swallows up Boss Borot and makes its way towards Tokyo. This Premiered 7-18-1976
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The series also had its own sequel movie entitled UFO Robo Grendizer the same as the series. No information avaiable at this time as to the plot of the movie which Premiered 12-20-1975
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One additional Spin off movie came out entitled UFO Robo Grendizer tai Great Mazinger in which alien invaders take over Great Mazinger who is at the entrance of a museum next to Mazinger Z as symbols of peace. Grendizer fights the evil invaders and great mazinger is recovered. It Premiered 3-20-76.

All the movies, spinoffs, were all shorts lasting around 3