During World War I, a German U-boat sinks a British ship and takes the survivors on board. After it takes a wrong turn, the submarine takes them to the unknown land of Caprona, where they find dinosaurs and neanderthals.
A group of scientists are sent on a mission to destroy unstable planets. Twenty years into their mission, they have to battle their alien mascot as well as a "sensitive" and intelligent bombing device that starts to question the meaning of its existence.
A prank that starts with a group of college students creating a fictitious person so they can get a credit card develops into a plot that leaves three of them dead.
Dr. Roger Girard is a rich scientist conducting experiments on head transplantation. His caretaker has a son, Danny, who, although fully grown, has the mind of child. One day an escaped psycho-killer invades Girard's home, killing Danny's father before being gunned down himself. With the maniac dying and Danny deeply unsettled by his father's death, Dr. Girard decides to take the final step and transplant the killer's head onto Danny's body.
Earth is invaded by an interstellar terrorist group, Big Fire (the Gargoyle Gang in the American version), led by Emperor Guillotine who spends most of his time in a multicolored space ship hidden at the bottom of Earth's ocean, from which he issues his orders. Big Fire is capturing scientists to create an army of monsters to conquer Earth. A boy named Daisaku Kusama (Johnny Sokko in the American version) and a young Unicorn agent named Jūrō Minami (Jerry Mano in the American version) are shipwrecked on an island after being attacked by a sea monster and subsequently captured by Big Fire. They flee to where a Pharaoh-like giant robot is being built by captive scientist Lucius Guardian, who gives Daisaku and Jūrō its control device. Guardian helps them escape before he is shot to death; before he dies, he triggers an atomic bomb which destroys the base. The radiation activates the robot, which now obeys only Daisaku.
In the hazy aftermath of World War III, the fallout from a 'nuclear misunderstanding' is producing strange mutations amongst the survivors, and the noble Lord Fortnum finds himself transforming into a bed sitting room.
Two young boys sneak aboard a spaceship and find themselves whisked away to the mysterious planet Terra. There, they encounter Gamera's old foe Gyaos and two female aliens with a taste for human brains. Gamera must save the children and battle the new monster Guiron, whose entire body is a deadly living weapon.
After a criminal gang kidnaps a scientist with valuable information about nuclear weapons, an undercover agent named Jorge Rubio tries to infiltrate this gang in order to deal with the situation. The gang, however, quickly unmasks Rubio and uses both brainwashing and torture techniques on him. They also create a clone of Rubio, thus setting up a show-down battle between the two look-alikes.
A groups of astronauts crash-land on Venus and find themselves on the wrong side of a group of Venusian women when they kill a monster that is worshipped by them.
As alien invaders plot to conquer the Earth, two Boy Scouts steal a mini-submarine and discover Gamera in their midst. Transported to the alien's spaceship, the Scouts are menaced by the evil inhabitants, including Viras, a squid-like monster that grows to colossal size to battle Gamera.
Scientists must prove their time travel experiments can produce results, so their funding won't be cut off. They push their equipment, and travel 5000 years into the future, where they encounter aliens who are looking for a planet to colonize.
While covering a test of guided torpedoes, two reporters believe they see what appears to be a strange-looking swimming creature. They investigate the matter further and discover that there is a race of fish-men living under the sea. The fish-men capture the pair and keep them prisoner in their underwater city.
When scientists use eco-terrorism to impose their will on the world by affecting extremes in the weather, Intelligence Chief Cramden calls in top agent Derek Flint.
In 2020, after the colonization of the moon, the spaceships Vega, Sirius and Capella are launched from Lunar Station 7. They are to explore Venus under the command of Professor Hartman, but an asteroid collides and explodes Capella. The leader ship Vega stays orbiting and sends the astronauts Kern and Sherman with the robot John to the surface of Venus, but they have problems with communication with Dr. Marsha Evans in Vega. The Sirius lands in Venus and Commander Brendan Lockhart, Andre Ferneau and Hans Walter explore the planet and are attacked by prehistoric animals. They use a vehicle to seek Kern and Sherman while collecting samples from the planet. Meanwhile John helps the two cosmonauts to survive in the hostile land.
Martians fear their children have become lazy and joyless due to their newfound obsession with Earth TV shows. After ancient Martian leader Chochem suggests that the children of Mars need more fun—including their own Santa Claus—supreme leader Lord Kimar assembles an expedition to Earth. Once there, they kidnap two children who lead them to the North Pole, then capture the real Santa Claus, taking all three back to Mars in an attempt to bring the Martian children happiness.