Destroy All Monsters

From Wikizilla

It's the year 1999 and all of Earth's monsters have been collected and are living together on Monster Island. The monsters are kept on the island by special devices such as magnetic walls and metal cylinders that spray out gas that repels the monsters. All of this is controlled from a base deep below the island's surface. All was going just fine on the island until the command center and the surface of the island are coverd in a strange knockout gas that takes out both the monsters and the humans on the island. A few days later, the monsters from the island begin to appear in major cities throughout the world... Godzilla in New York, Rodan in Moscow, Mothra in Beijing, Gorosaurus in Paris, Manda in London, etc. Only Tokyo being spared from these attacks. The spaceship Moonlight SY-3 is recalles from the moon to investigate the island, but the crew finds the base surprisingly operational and aliens calls the Kilaaks say that they are taking over the world with the humans and the monsters are under their control...

Trivia

During Godzilla: the Series, there was a 3-part story arc called Monster Wars. During these episodes, aliens known as the Tachyons appeared and took control of the monsters of Earth. They are eventually defeated and their base of operations is turned into Site Omega or, as it is more commonly called, Monster Island. Also, elements from both Destroy All Monsters and Monster Wars were used in Godzilla: Final Wars, where a race called the Xiliens came, took control of Earth's monsters and used them to attack major cities.

Note

• This film is said to be a remake of Invasion of Astro-Monster.
• Greatest number of kaiju species appeared in one Godzilla movie of Showa series.