* ContestWinnerCameo: The entire script, though it was changed so much only the following aspects were kept: the death of Dr. Shiragami's daughter, Biollante's creation, a psychic girl, and the general ending.
* HeyItsThatGuy:
** Yasuko Sawaguchi, the actress who played Naoko in ''Film/TheReturnOfGodzilla'', portrays Erika Shiragami here.
** Former JPop singer Yoshiko Hidaka who also starred in ''Film/BlackRain'' has a role in the film.
** Katsuhiko Sasaki, who played Goro the inventor and Ichinose in the Showa series has a bit part as some random military personnel. He gets a bigger role in ''Film/GodzillaVsKingGhidorah'' though.
* WhatCouldHaveBeen:
** The film was originally written by a Japanese Dentist and featured a far different story than what the film is today. The film was to focus heavily on Dr. Shiragami as he creates both Biollante and a rat/fish hybrid monster named "Deutalios" out of insanity due to her daughter Erica's death. Godzilla would've fought, killed, and eaten Deutalios and would've fought Biollante until retreating due to injuries. However it was felt that Godzilla was given very little focus in the story, and so re-writes were made: replacing Deutalios with the Super-X2 and a rose form of Biollante, and Godzilla being injected with Anti-Nuclear Bacteria to slowly kill him.
** In the script and or an earlier draft, Miki was supposed to psychokinetically levitate Godzilla, but Tomoyuki Tanaka apparently wasn't fond of the idea.
** In another ending, a losing Biollante would have tried to kill Godzilla by turning into a wave of pure energy.
** One idea for Biollante's final design in the film was a flower with human face in the middle that talked.