It all started with Getter Robo (1974), which gets my vote for greatest robot anime theme song EVER.
Getter Robo G (1975) rehashed the song. Known as “Starvengers”
From now on it’s alternate universe after alternate universe…
Getter Robo Go (1991) drew a mixed reaction from fans
There was a traditional super-roboish song…
… and a 80s-90s “pop songish” song
Getter Robo Armageddon or (Shin Getter Robo: The Last Day of the World) (1998)
Heck, there was even a videogame
Then there was Shin Getter Robo vs Neo Getter Robo (2000)
And Shin (New) Getter Robo (2004)
Okay so it was mirror imaged to prevent copyright infringement thingees, I was told.