BetweenGodzillaand King Kong’s 1962 and 2021 meetings, there was a series of three known attempts to bring the two back together again. Created in 1939 and 1954 respectively, King Kong and Godzilla have shared the big screen a total of three times over a 71-year period of shared cinematic history. After RKO and Toho arranged Godzilla and King Kong’s famous clash in 1962’sKing Kong vs. Godzilla, decades passed before a rematch could be worked out.
Legendary’sGodzilla vs. Kongnotably renewed their rivalry by pitting the Monsterverse incarnations of the characters against each other. Rather than go back to their separate ways like their Toho counterparts all those years ago, Godzilla and Kong reunited again just three years later inGodzilla x Kong: The New Empire’sending. What’s more, a fourth partnership is expected in theuntitledGodzilla x Kongsequel. But had previous efforts for Godzilla-Kong crossovers gone differently, their next team-up could have been their seventh meeting.

Continuation: King Kong vs. Godzilla
The Movie Would Have Been A Direct Sequel To Their First Crossover
Similar to how Legendary moved on fromGodzilla vs. Kongand straight toGodzilla x Kong, Toho once had a mind to do this as well. On account of the first crossover’s success, Toho had discussions about an immediate follow-up wherein the two would have a rematch. TitledContinuation: Godzilla vs. Kong, the treatment would have been a direct sequel that picked up after the events ofGodzilla’s apparent defeat. Godzilla’s body would have washed up on the shore, with the human characters wrongly assuming he’s dead for a large portion of the film.
It also would have reversed the human characters' plan inKing Kong vs. Godzillaby having them work toward reviving Godzilla with electricity to fight King Kong.

The lead-up to Godzilla’s awakening and inevitable rematch with King Kong would have consisted of a fight between Kong and a giant scorpion and the introduction of a monster amusement park. It also would have reversed the human characters' plan inKing Kong vs. Godzillaby having them work toward reviving Godzilla with electricity to fight King Kong. At the end of the movie, the fight would have concluded with the two being trapped in a volcano.
Of course, the movie didn’t move forward, with Toho opting to makeMothra vs. Godzillanext instead. No official reasoning for the sequel not coming to fruition has been offered, but as noted by John LeMay’sThe Big Book of Giant Japanese Monster Movies: The Lost Films,the story was extremely similar to the first movie, so much that Toho may not have considered it worthwhile.

Destroy All Monsters (1967 Version)
There Were Multiple Drafts Of The Destroy All Monsters Script, Some With Different Kaiju
In 1968, Toho releasedDestroy All Monsters,an Avengers-esque crossover where Godzilla and a slew of kaiju from other Toho monster movies joined him in a fight against King Ghidorah. Monsters with pre-existing connections to Godzilla - such as Angurius, Rodan, and Mothra - were on hand, including monsters from standalone films, including Baragon, Varan, and Manda. But though it had an impressive lineup, it was actually supposed to be much bigger. An earlier draft of the script would have seen King Kong take part in the fighting as well, presumably as an ally against Ghidorah.
WhileDestroy All Monsters did not bring Kong back afterKing Kong Escapes, it did feature Gorosaurus, one of his two opponents in the movie.

BecauseToho viewedDestroy All Monstersas an “all-hands-on-deck” type of story, it wanted all of its monsters involved, and that approach included, in addition to the monsters seen in the final version, King Kong and both Sanda and Gaira fromWar of the Gargantuas. King Kong’s appearance would have been fresh off his role in 1967’sKing Kong Escapes. However, it would seem thatDestroy All Monsterstook a bit too long to make. The five-year licensing agreement that allowed Toho to use Kong eventually ran its course, resulting inKing Kong Escapesbeing his last Toho film.
King Kong vs. Godzilla (1991 Version)
Toho’s interest in Godzilla-King Kong crossovers cooled off after it lost the rights, but heated up again in the early 1990s when Godzilla’s Heisei series was ongoing. AfterGodzilla vs. Biollanteperformed poorly at the box office, Toho pivoted back to a more recognizable franchise name for his next opponent and madeGodzilla vs. King Ghidorah. Prior to settling on that matchup, Toho entertained a pitch from Shinji Nichikawa, who proposed a remake ofKing Kong vs. Godzilla. It makes sense that Toho was interested in the idea, considering how much attention the film would have received.
The Monsterverse Wouldn’t Exist Without This Unmade Sequel To A 1971 Godzilla Movie
A failed plan to make a sequel to a 1971 Godzilla movie is ultimately what paved the way for Legendary’s Monsterverse to be born in 2014.
Based on what’s been established about the plot for the remake, King Kong would have lost their first fight before getting transformed into a cyborg for the final battle. If this plot sounds familiar, it’s because this is the direction that Toho ultimately went with forGodzilla vs. King Ghidorah. So while Toho may not have gone ahead with this plan, it looks like this aspect of the story was recycled into itsGodzillanext project via Mecha-King Ghidorah. As for why it didn’t happen, LeMay’s book suggests that the rights to King Kong may have been deemed too expensive for Toho to purchase at the time.