UFO Robo Grendizer tai Great Mazinger
Genres: Sci-Fi
Type: Movie, Episodes: 1
Aired: Mar 20, 1976
Studio: Toei Animation
Source: Unknown
Rating: PG-13 - Teens 13 or older
Synopsis:
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)