Toho considered introducing a new fire-themed kaiju for REBIRTH OF MOTHRA III. However, Toho ultimately decided to use a popular existing monster instead. Originally, Rodan was to be the villain, while Mothra Leo would have traveled back in time to medieval Japan to fight him.

A solo King Ghidorah movie targeted for a 1999 release date had been planned since at least 1995 according to Koichi Kawakita. Instead, the three-headed kaiju was worked into REBIRTH OF MOTHRA III as the film's antagonist.

While King Ghidorah is alluded to as the "King of Terror," the film was originally going to more explicitly tie him into Nostradamus' prophecy. Additionally, he was originally going to be revealed as Desghidorah's father.