Captain Future is Curt Newton, a brilliant scientist and athlete who helps the helpless with the assistance of Simon Wright, a scientific colleague of his father's who is now a Brain in a Jar, and two robots created by Wright and Newton Sr.: Grag, a seven-foot-tall Dumb Muscle man of metal, and Otho, a shape-shifting Artificial Human.
The series was also popular in Japan, where it inspired a 1967 tokusatsu series (under the title Captain Ultra, as it was commissioned as a filler for the Ultra Series timeslot) and a 1978 anime. Sci-fi writer Allen Steele has also written an Origin Story reconstruction novel Avengers of the Moon.
This series contains examples of:
- A.I. Getting High: Otho the android drains a bottle of Gargle Blaster to no visible effect while undercover... and then asks for wine with radium chloride. This time, the radiation does get him intoxicated.
- Alien Catnip:
- One of the characters has a pet called Eek who eats metals, preferring heavy ones. Large doses of silver or gold were shown to make him rather drunk.
- In one of the books, Otho, disguised as a human, goes to investigate in a bar. First, he drinks a bottle of Gargle Blaster without any visible effect, then he orders wine... laced with radium chloride. That one works.
- All Planets Are Earthlike: Taken to an extreme, with Earth's moon being perhaps the only exception. All of the Solar System's planets are Earth-like, and harbor humanoid life. The planets' moons also often harbor Earth-like life — at one point, Captain Future encounters a Giant Spider on Leda, one of Jupiter's moons.
- America Takes Over the World: President James Carthew runs the entire solar system from his office in New York City. The Allen Steele reconstruction justifies this by having it on the site of the old United Nations building.
- Arch-Nemesis: Ul Quorn, the 'Magician of Mars', an evil genius whose intellect is a match for Captain Future. He's also the son of Victor Corvos who murdered Curt's parents and was killed in turn by the Futuremen, so It's Personal for both of them.
- Bat Signal: Captain Future is summoned from his secret Moon base by a magnesium flare fired from the North Pole.
- Brain in a Jar: Simon Wright. A distinguished but elderly scientist, he had his brain transplanted into an artificial case before his body gave out. At the beginning of the series the case is immobile and has to be carried around by the Robot Buddy; later it gets an upgrade and is able to hover around under his direction.
- Captain Superhero
- Charles Atlas Superpower: Having been raised with Otho and Grag as sparring partners, Captain Future is more than a match for any human opponent, and the Brain's education has turned him into an Omnidisciplinary Scientist.
- Conveniently Unverifiable Cover Story: In Outlaw World, Captain Future temporarily ends up with some pirates, and pretends to be a survivor from a recently destroyed band.
- Death by Origin Story: Curt's parents, both scientists, were murdered by power-hungry politician Victor Corvos who wanted to steal their biochemical knowledge for his own schemes. Unfortunately for him Ortho and Grag prove to be Immune to Bullets and quickly avenge their creators, leaving Curt to be raised by them and Simon Wright.
- Derelict Graveyard: One of the books is titled "The Sargasso of Space." It's about an eponimous region of space into which currents of aether tend to drag all kinds of ship wreckage.
- Earth All Along: In Planets in Peril, Captain Future goes to help a human looking race in a dying universe (a short time away from being reborn in a new Big Bang). In the end, it is revealed that the universe is actually our own some 20 billion years in the future.
- Gargle Blaster: Jovian fire-liquor. The description is "One ounce of it, and you think a meteor's hit you. Two ounces, and you think you're a meteor yourself." Otho the android is unaffected.
- Genuine Imposter: In Planets in Peril, Captain Future goes into an alternate universe to impersonate an ancient hero who promised to return when needed. The ending reveals the alternate universe to actually be Earth All Along, with which information it becomes apparent that the ancient hero's name, Khaffr, is a half-recalled distortion of "Captain Future".
- Giant Spider: Captain Future encounters some on some of the Solar System's planets.
- Handy Feet: The android Otho once shot a blaster with his feet when chained.
- Humanity Came From Space: From Deneb, to be precise. There are other colonies all over the Solar System and beyond.
- I Am One of Those, Too: In Outlaw World, Captain Future temporarily ends up with some pirates, and pretends to be a survivor from a recently destroyed band. Then, they visit the pirates' main den, and one person states he served in that band for nine years and had never seen him. The Captain buys a reprieve by claiming he was a freshly recruited technician, and had no opportunity yet to interact with a gunner.
- King in the Mountain: In Planets in Peril, Captain Future is convinced to go into a parallel universe and impersonate an ancient hero who promised to come back when needed. In the end, it is revealed he didn't go into a parallel universe, but his own twenty billion years in the future, and the legend he has been impersonating is based on himself.
- Lotus-Eater Machine: A villain named Ru Ghur discovered a type of radiation capable of doing that. He denied it was anything bad, but people were apparently a bit too desperate to get another dose.
- Love Interest: Joan Randall of the Planetary Police.
- Master of Disguise: With the help of a chemical, Otho can mold his face to mimic any individual.
- My Brain Is Big: Doctor Zarro.
- Never Gets Drunk: While Otho is supposed to be organic, his metabolism is powerful enough to drain a bottle of the Solar System's strongest Gargle Blaster to no effect.
- Oblivious Astronomers: Calling Captain Future begins with a Do Not Adjust Your Set moment where a mysterious person warns of a danger; an incoming dark star that will destroy the Solar System unless all its resources are entrusted to him to avert the danger. The star is already close enough to be seen through an amateur's telescope, yet the professional astronomers have noticed nothing, so naturally, after this kind of blunder no one trusts them when they say it's merely a low-mass dust cloud. Subverted at the end; it's nothing but an enormous hologram, so naturally nothing could be detected until the projectors were turned on.
- Rapid Aging: In one story, a gang was selling water from a radioactive spring which made people young. Too long without the water, and the person died from rapid aging. There was actually an attempt to give a scientific explanation; the body no longer has the resources and regeneration of a young person, but continues expending them like one.
- Ray Gun: The hero's proton blaster is shown on the pulp covers shooting a stream of ever-expanding rings. In the Allen Steele novel this is handwaved as smoke rings created by the invisible plasma beam.
- Reconstruction: Avengers of the Moon by Allen Steele acknowledges that Technology Marches On (for instance the Comet can't do Casual Interplanetary Travel — it's ferried to Mars by a Solar Sail Mother Ship) and Society Marches On (Grag and Otho don't call Curt 'Master'; in fact there's a Fantastic Racism theme) but keeps the pulp Space Opera feel. There are also several Reality Ensues moments — a young man raised in isolation would find it difficult to interact with attractive women, for instance.
- Retro Rocket: The cyclotron-powered Comet (though not in the anime where it's an ISO Standard Human Spaceship).
- Strapped to a Rocket: One of the Pulp Magazine covers involved the hero's Love Interest strapped to a small Retro Rocket while his Robot Buddy tries to cut her free. A later edition had her inside the one-woman rocket, peering out through a transparent plate as Captain Future fired his raygun at a villain about to pull a large lever, presumably to send her off.
- Super Hero: Captain Future is quite a textbook example, being stronger, smarter, and more agile than any other human being in existence, and being also an Omnidisciplinary Scientist who is more knowledgeable than the leading scientists in any given field. His team of sidekicks isn't far behind.
- Teeth-Clenched Teamwork: Ortho and Grag are always arguing over which one is superior.
- Three Laws-Compliant: Averted as the stories began before the Trope Namer. Grag has no problem obeying an order to kill those who murdered his masters.
- Touch of the Monster: One famous pulp cover has Grag of all characters clutching a woman in a metal bikini while fending off someone offscreen with its raygun. Another cover plays it straight with Curt firing on a Tin-Can Robot who's in the process of picking up a Damsel in Distress.
- Turned Against Their Masters: Cold Ones, beings created by a human scientist to be humanity's successors when the stars started going out. They turned out: 1) Always Chaotic Evil and 2) incapable of surviving in a normal universe — and the scientist's dying universe was supposed to be reborn in a new Big Bang in a few thousand years. When the scientist tried to destroy them and start anew, they killed him and then tried to eliminate mankind. By the time our heroes arrive, humanity has been reduced to mere millions on a few planets, and the Cold Ones are giving them a choice between extermination and sterilization.
- Villain Song: Some of the books have a few lines from the Space Pirates' anthem:From Mercury to Pluto,
From Saturn back to Mars,
Well fight and sail and blaze our trail
In crimson through the stars!
Well cram our holds with plunder
From every world and moon...
- Vitriolic Best Buds: Grag and Otho.
- Weird Science