It's worth noting that some monsters associated with Godzilla actually did start out as their own solo acts, with big names like Mothra or Fire Rodan existing in their own independent giant monster movies before being brought aboard to Godzilla's universe. However, it's the canceled Godzilla movies that could have really filled out these titanic creatures' backstories or solo efforts a bit more, sadly falling through as so many other Toho kaiju films did before and after. It's a shame these monster movies didn't have the chance to expand on Godzilla's less-famous coterie of beasts.

6 Ebirah

Operation Robinson Crusoe: King Kong vs. Ebirah

By far the most famous Godzilla collaborator, King Kong's various films have padded out a well-identified roster of different stories, some of them spearheaded by Toho themselves. Films like King Kong Escapes put Kong up against his own unique villain, Mechani-Kong, and another movie nearly reserved what would become a Godzilla enemy for the iconic American simian. Enter Ebirah, who was slated to first appear in the planned Operation Robinson Crusoe: King Kong vs. Ebirah.

Ebirah is a sea monster who looks like a massive spiky crustacean, complete with formidable claws. King Kong was originally planned to face him and Mothra sans Godzilla, but the movie was re-tooled into Ebirah, Horror of the Deep, which more-or-less lifted the same plot of Operation Robinson Crusoe: King Kong vs. Ebirah but subbing Kong for Godzilla. Ebirah made a couple of other small appearances in All Monsters Attack and Godzilla: Final Wars, but never recieved title billing again. It's a shame he wasn't able to share the spotlight with King Kong.

5 Jet Jaguar

Jet Jaguar vs. Megalon

One of the most striking good guys in Godzilla history, Jet Jaguar has to be one of the friendliest and humanitarian allies Godzilla ever shared the screen with. Heavily influenced by Tokusatsu heroes like Ultraman, Jet Jaguar is a size-changing robot superhero known for his gleaming grin and flamboyant poses. Jet Jaguar was actually the result of a Toho-held fan contest to create a new monster, capitalizing on the popularity of giant robot media at the time. His powers include flight, shrinking, growing, and firing laser beams.

Jet Jaguar was originally planned to go head-to-head with the subterranean insectoid kaiju Megalon in Jet Jaguar vs. Megalon. However, Toho worried that Jet Jaguar wouldn't be a promising enough character to carry a film on his own, and reworked the title into Godzilla vs. Megalon, which turned the fight into a two-on-two tag team battle with Godzilla and Jet Jaguar on one side and Megalon and Gigan on the other. Godzilla vs. Megalon is a great movie, but it would have been interesting to see how Jet Jaguar's legacy would have progressed if left to his own devices.

4 Mothra

Mothra vs Bagan

Interestingly enough, Mothra is one of the few non-Godzilla Toho monsters iconic enough to already have her own solo film. Mothra's roots actually extend to literature, first appearing in the 1961 novel The Luminous Fairies and Mothra, which was adapted shortly after its release into the movie Mothra. A few decades after that, the benevolent moth goddess even received her own dedicated series with the Rebirth of Mothra trilogy, capitalizing on her appeal as Toho's second-most-popular kaiju.

The filmography of Mothra was nearly expanded by one with the canceled film Mothra vs Bagan. This planned movie would have seen Mothra go up against the ancient Chinese demon Bagan, a character that had been conceptualized years earlier in drafts for another canceled film, Resurrection of Godzilla. The film would have allowed Mothra to team up with one of her larval forms, emphasizing her more humanitarian nature compared to Godzilla. Ultimately, the film fizzled out due to the poor box office performance of Godzilla vs. Biollante. Bagan would unfortunately never end up finding his way into another movie.

3 Hedorah

Hedorah vs Midora

Considering the cliffhanger ending implying a return that Godzilla vs Hedorah ended on, it's surprising that the smog monster was never able to manifest a feature-length dedicated return. Hedorah is an alien life form that arrived on Earth via comet and absorbed the pollution of humanity, looking like a bizarre shambling mound of filth that can turn itself into a flying UFO form. While the planned Godzilla vs Hedorah 2 never came to fruition, Hedorah showed up in ensemble films like Godzilla: Final Wars and Godzilla Island.

One of the more sympathetic of Godzilla's villains, Hedorah almost got the chance to headline a film via Hedorah vs Midora. Director Yoshimitsu Banno had a great deal of fondness for Hedorah, conceptualizing a story in which it was revived by nuclear energy and confronted by a new plant-like kaiju, the heroic Midora. Apparently, a young girl with a pet slug were also integral to the plot. Tragically, Banno ed away before his ambitions for the ugly, yet strangely cute slime monster could be realized.

2 King Ghidorah

Untitled King Ghidorah film

Of all of Godzilla's villains, King Ghidorah is perhaps his single most iconic foe. The rivalry between Godzilla and King Ghidorah extends all the way back to his first appearance in 1964's Ghidroah, the Three-Headed Monster, which introduced the intimidating golden dragon as a ferocious force to be reckoned with and a tyrannical alien destroyer. In various films, his origins story has been reworked and tinkered with, sometimes describing him as more of a weaponized creature genetically engineered from three monsters by time-travelers or a mutant from outer space.

In 1999, Toho planned to release an Untitled King Ghidorah solo film, special effects director Koichi Kawakita in a 1995 interview. Other than its existence, however, absolutely no details about the film are known, let alone which origin story for King Ghidorah of the many available the project might have moved forward with. If there's one Godzilla antagonist iconic enough to be deserving of his own solo film, it's King Ghidorah.

1 Kiryu

Type-3 Kiryu

There have been many incarnations of Mechagodzilla over the years, but perhaps none of them are as cool or memorable as the ferocious Kiryu of the Millennium series. First appearing in 2002's Godzilla Against Mechagodzilla, Kiryu is a cybernetic creation built around the bones of the original 1954 Godzilla, whose latent consciousness eventually emerges to wrestle control from its human pilot and go on a rampage. After his second appearance in Godzilla: Tokyo SOS, a solo movie titled Type-3 Kiryu was pitched.

Named after his official combat designation, Multipurpose Fighting System Type-3, Kiryu's solo film is shrouded in mystery. Perhaps the film would have brought him back from the depths of the sea after he sacrificed himself to avoid killing his organic counterpart in Godzilla: Tokyo SOS, or even proposed a new origin for the mechanical creature entirely. Either way, Type-3 Kiryu is one of the most bitterly wasted pieces of potential in the unmade Godzilla movie canon.