Invasion of Astro Monster (1965)
Astronauts encounter the Xiliens, who ask Earth to rid their planet of Monster Zero, but when one astronaut romances a mysterious woman, he uncovers the Xiliens true intentions
Son of Godzilla (1967)
A reporter stumbles upon weather experiments on a tropical island, discovering giant mantises, a castaway woman, and an infant monster that Godzilla must learn to raise as a son
Destroy All Monsters (1968)
In 1999, a race of she aliens, the Kilaaks, brainwash Earths monsters into attacking major cities, prompting a team of astronauts to stop the invaders while the monsters battle Ghidorah
Space Amoeba (1970)
A space probe is infiltrated by alien beings and then crashes on a remote Pacific atoll A group of people discover it to be inhabited by giant mutant monsters, created by the aliens in an attempt to conquer the world