 This movie was originally intended to be Godzilla vs. GhostGodzilla  where Godzilla will fight the ghost of the original one. TOHO then  changed its mind because the last two movies had Godzilla in the  enemys name (MechaGodzilla and SpaceGodzilla). TOHO decided to  bring back the Oxygen Destroyer to fight Godzilla instead of the  GhostGodzilla.