As one of the main selling points of their films, Toho Studios has spent a vast majority of their time crafting monsters of various quantity and quality to be involved in their films whether it be in their main Godzilla series or their other features. While Godzilla has remained their big money-maker and longest-lasting series, that there have been other attempts at creating these kinds of movies that have meant the need for crafting either allies or opponents for these films over the years. Some are better than others, but when they hit a great idea for a creature or concept it should make sense to reuse the particular creature over and over again, such as with popular beasts like Anguirus, Rodan, King Ghidora, and Mothra, to name just a few. That makes it even weirder how some of the creatures were never given another shot as they provided a lot to like within their specific film even though they managed to leave an impression.
That means we can look at some of the best one-shot creatures that have been brought up in the following list. We will do so with a couple of caveats, in that first the creature in question must only appear in one film, whether it be in a traditional Godzilla film or a different film entirely. Secondly, the creature must not be a variation of a creature in a different lineage, meaning that infant versions in an evolutionary sense. This is a way of saying that, even if they only appeared in one film, Baby Godzilla, Little Godzilla, and Godzilla Junior as well as Godzillasaurus won't be included as they're involved in an evolution of the same creature.
With that said, let's get on the list.
10. Sanda/Gaira (War of the Gargantuas, Ishiro Honda)
While it might be a slight cheat to have them together immediately as a pair, there's a sense of synergy to having them both together here. With Sanda the gentle Brown Gargantua and Gaira the vicious Green Gargantua, the two are impressive designs following the type of humanoid design from “Frankenstein Conquers the World” the year prior. Featuring a different enough look so that there's a way to tell who they are even without the body color is a giveaway, there's very little reason why they managed to only survive the one film as the costumes were brilliant and able to be repeated several times over in different films.
9. Biollante (Godzilla vs. Biollante, Kazuki Omori)
A massive flowering plant-like creature that's able to shift its appearance like several other creatures on this list, this one at least scores some points since it does manage to get brought up in continuity for several films following it. Still, the physical appearance here is missing in those later films, so Biollante is still a one-time appearance which is a bit of a shame since this plant-like creature has some intriguing qualities involving its enormous bulk, invulnerability to most of Godzilla's attacks, and creative concept provide a rather solid basis to show off in repeat engagements.
8. Destoroyah (Godzilla vs. Destoroyah, Takao Okawara)
A shapeshifting crustacean creature that has the benefit of multiple designs to choose from, this massive beast is a rare case where it's origin status in “Destoroyah” also explains why it hasn't appeared again. The series of impressive designs here, whether it's the crab-like form, flying variation, or bipedal design, cry out to be brought back again although the origin story tying it so exclusively to the original Oxygen Destroyer as a spawning point could be something to be changed in return engagements. Still, there's enough at work here to warrant a chance for the creature to return in some capacity.
7. Orgah (Godzilla 2000: Millennium, Takao Okawara)
A bizarre and misshapen being that features a unique backstory alongside its unconventional design, this creature is a case where the inability to focus on its history is due to factors beyond its control. Since Orgah appears on-screen only to then get into a fight moments later before being dispatched, there's no real chance to dive into anything about it so the chance to dive into a different origin to explain some of the peculiarities about it such as the grotesquely oversized hands, unusual body proportions, and unexplained powers it demonstrates would provide a chance to get to know it better.
6. Battra (Godzilla vs. Mothra, Takao Okawara)
This special creature, almost strictly operating as a sole ‘evil Mothra' motif, takes the concept and design of Mothra and adds a dark Gremlin energy to everything so it appears to be a direct rip-off of the creation. That does limit its specialness quite significantly as there's not much difference once you start looking at the creature and its differences, yet it also serves as the perfect backup option for people who are far more burnt out on the company continually using Mothra to have Battra as a potential fill-in. That it never got brought up again is a shame even though it is the most understandable one.
5. Megalon (Godzilla vs. Megalon, Jun Fukuda)
This giant subterranean beetle-like creature is certainly a sign of the times it came off with the sheer lunacy of its concept and appearance creating a memorable monster. The unique appearance, including its insect features, massive star-shaped horn, and rotating drills for hands, have given it a grand design that fans have gravitated to recently and seem to cry out for a return trip to theaters. It's more of a cult choice than anything as most might write off the creature due to the quality of the film it's from, but a bizarre design and hints of a personality in its lone appearance might be deserving of a return to the franchise.
4. Megaguirus (Godzilla vs. Megaguirus, Masaaki Tezuka)
Another flying insect-like similar to Battra mentioned above, this particular creature is slightly higher as it doesn't have the stigma of its concept being so similar to another creature that just so happened to be in the same film with it weighing against it. Still, they're rather similar with an impressive design, effective special effects to bring it to life, and an inventive backstory that can be utilized quite effectively in numerous other films afterward that all can come into play should this be revived in the future. It even manages to come from a good enough film that would score points for it to come back.
3. Space Godzilla (Godzilla vs. Space Godzilla, Kensho Yamashita)
A newer monster, this creature has quite a lot to like about it. An impressive backstory involving the beast being born from Godzilla's cells entering outer space and merging with crystalline life form, an enjoyable design, cool effects to bring it to life, and a very imposing design help to make this an unfairly maligned creature. This might be a case where the depth of quality of the film itself might be a reason why it's never returned in a follow-up as it's not a good film in any sense, but the fact that the creature itself is a major highlight should be a cause for bringing it back somewhere down the line.
2. Mechanikong (King Kong Escapes, Ishiro Honda)
Among the studios' most beloved designs, this massive robot is almost literally a personification of its name, being a robotic version of King Kong, it provides plenty to like about it, with its impressive design, and unique backstory that can easily be altered to bring it back, and general sense of aura that's employed whenever it's on-screen. With their own version of King Kong at their disposal, how it never appeared again to overcome the admittedly superior Mechagodzilla fatigue is a mystery as these cry out for a new adaptation and updated design for a brand-new adaptation should it return.
1. Titanosaurus (Terror of Mechagodzilla, Ishiro Honda)
This massive dinosaur-like creature is the final choice, as it's a crying shame that it only got one appearance in the series that seems to hint a return appearance would be in the cards. In the storyline introduced as a gentle creature but forced to be a vicious brute at the hands of its captors in their world-domination plans, it coming back under it's more traditional manner and mindset would be quite appropriate to see being on the good side. That setup screams for a return of the creature, as the incredible physique, unique look, and creative powers would be a fine touch to update and bring back into a new generation.