Destroy All Monsters (1968)

At the end of the 20th century, the United Nations Science Committee has captured and contained all of Earth's monsters on an island located in the Ogasawara chain dubbed "Monsterland." The island is monitored from a special underground control center staffed by scientists who ensure the monsters stay secure and also study them. One day, a cloud of knockout gas suddenly appears over the island, knocking the monsters and the human researchers all unconscious. Soon after, the monsters begin to appear in major cities across the globe: Godzilla attacks New York, Rodan appears in Moscow, Gorosaurus destroys Paris, Mothra terrorizes Beijing, and Manda assaults London. With communications with Monsterland mysteriously severed, the UNSC sends Katsuo Yamabe and the crew of the Moonlight SY-3 to end their patrol on the Moon and investigate the island. They find the island badly damaged and all of the monsters gone. Yamabe and his men enter the research base under the island and find the staff all alive, but acting strangely. Lead researcher Dr. Otani and Yamabe's sister Kyoko bring the SY-3 crew further into the base and introduce them to a group of mysterious women wearing silver robes. The leader reveals that she represents the Kilaaks, an advanced race of aliens that have come to stake their claim on Earth, and that they have used mind control to turn all of the Monsterland staff as well as the island's resident monsters into their servants. The Kilaak Queen demands that the human race surrender to her race immediately, or else they will be forced to annihilate human civilization. Yamabe and his men refuse and open fire on the Kilaaks, but find they are defended by a forcefield. The Kilaaks escape and order their mind-controlled slaves to kill Yamabe and his men. The SY-3 crew fights its way through the Kilaaks' servants and manages to escape the island with Dr. Otani. Otani is brought to a UNSC base and interrogated by Yamabe and Dr. Yoshida, but refuses to reveal any details about the Kilaaks' plan. While Yamabe and Yoshida are talking in another room, Otani commits suicide by jumping out of a nearby window. Kyoko and a group of Kilaak-controlled armed men arrive to recover Otani's body, but are attacked by the UNSC's special police force and retreat. The UNSC conducts an autopsy on Otani, and discover a strange device implanted in his head. They quickly determine that this must be how the Kilaaks are controlling Otani and the others.

With the world's attention drawn away from Japan, the Kilaaks establish an underground base near Mount Fuji and direct their next attack at Tokyo. Godzilla, Rodan, Mothra and Manda all attack Japan's capital at the same time, catching its defenses completely off guard and annihilating the city with little opposition. While Tokyo is destroyed, the UNSC manages to capture Kyoko and free her from the Kilaaks' control. Unfortunately, Kyoko has no memory of the Kilaaks' plans and cannot provide the UNSC with any useful information. Elsewhere in Japan, an old man discovers a bizarre device inside a rock found near a village. The UNSC analyzes the device and learns it is used to broadcast the Kilaaks' mind control waves over a certain area. Many other such devices are found all around the world, but the UNSC learns the Kilaaks have begun broadcasting their signals directly from a base under the lunar surface instead. Yamabe and his crew board the Moonlight SY-3 and embark on a desperate mission to the moon while the JSDF battles several of the Kilaaks' monsters near Mt. Fuji. The SY-3 arrives on the moon and its crew infiltrates the aliens' hidden base. After a fierce gunfight, the SY-3 crew destroys the Kilaaks' control device and damages the base's environmental controls, forcing the Kilaaks to revert to their true forms, metallic slug-like creatures. This reveals the invaders' weakness: low temperature. The Kilaaks thrive in artificially high temperatures, but will revert to their true forms if exposed to lower temperatures.

With the Earth monsters all freed from the Kilaaks' control, the UNSC directs them all to the Kilaaks' base at Mt. Fuji, intending to put an end to their invasion once and for all. The Earth monsters all arrive, led by Godzilla. As they approach, the Kilaaks unleash their trump card: King Ghidorah. The triped-domed destroyer lands amidst the Earth monsters and begins his attack. Godzilla, Anguirus, Gorosaurus, Mothra, Kumonga, and Rodan lead the counterattack while Minilla, Manda, Varan, and Baragon look on. Anguirus bites down on one of King Ghidorah's necks, but the space monster takes flight, with Anguirus still hanging on with all his might. King Ghidorah finally bites Anguirus on the neck with one of his free heads, sending him plummeting to the ground. Anguirus is buried in a ditch, and King Ghidorah promptly lands on top of him and stomps him into the dirt. King Ghidorah flies over to Godzilla and his other two attackers, while Anguirus shakes the dust off and re-enters the battle. The Earth monsters struggle against King Ghidorah until Gorosaurus delivers a devastating kangaroo kick to King Ghidorah's back, causing him to fall to the ground. Godzilla and Anguirus seize the opportunity and begin brutally stomping on King Ghidorah's necks, causing him to cough up blood. When only one of King Ghidorah's heads is left breathing, it is subsequently strangled by one of Minilla's smoke rings. Mothra and Kumonga then cover King Ghidorah's lifeless body in webbing. Refusing to admit defeat, the Kilaaks unleash a "burning monster" they call the Fire Dragon, which terrorizes the monsters before destroying the humans' control devices on Monsterland. Godzilla proceeds to the Kilaaks' base and blasts it repeatedly with his atomic breath, only for the base's shield to resist it. Godzilla then kicks through the base's shield and personally destroys the base, triggering a chain reaction explosion that consumes the entire base and opens a fissure under King Ghidorah's body, which falls in and explodes. The Moonlight SY-3 gives chase to the Fire Dragon, and successfully shoots it down, revealing it as a flaming Kilaak flying saucer. The Earth is saved at last, and the alien invaders are no more. The monsters are all returned to Monsterland to live out their days in peace. Yamabe and Kyoko accompany Dr. Yoshida in a helicopter which flies over the island. From the helicopter, they observe several of the monsters living peacefully on the island, including Godzilla and his son Minilla, who stare contently and roar at the chopper as it flies by.