UFO Robo Grendizer tai Great Mazinger
Japanese title: UFOロボ グレンダイザー対グレートマジンガー
Alternative titles: UFO Robo Grandizer vs. Great Mazinger
Type: Movie
Source: Manga
Episodes: 1
Status: Finished Airing
Aired: Mar 20, 1976
Duration: 24 min
Rating: PG-13 - Teens 13 or older
Studios: Toei Animation
Producers: Dynamic Planning
Genres: Action, Sci-Fi
Themes: Mecha

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. 

When the Vegan empire dispatches a new general to oversee the takeover of Earth, he quickly manages to capture Koji Kabuto and, learning of Great Mazinger through interrogation, quickly commandeers it from a museum where it was kept as a symbol of peace. 

It is now up to Duke Fleed aboard Grendizer to stop humanity's former defender from becoming its destroyer.

(Source: ANN)