This is almost definitely Ringworld by Larry Niven.
The mountain in question appears strange to Louis and company because it's so big, and it's located in the middle of the ring, while most of the mountains are part of the ringwall.
"That's the biggest tanj mountain I ever saw in my life."
He had spoken too softly. "A mountain!" he ...
This is probably Isaac Asimov's "Spell My Name with an "S"".
The story concerns Marshall Zebatinsky, a Polish-American nuclear physicist. He is concerned that his career has stalled, and in desperation consults a numerologist for advice on restarting it. The numerologist advises him to change the first letter of his name to "S": Sebatinsky.
Excalibur #58 (1992) fits the bill, your villain being Alchemy.
Trouble on both sides! With both the Crazy Gang and the trolls that kidnapped Alchemy on the loose, can even the combined strength of Excalibur and the X-Men come out on top?
As revealed in the previous issue, Alchemy was in with the trolls who used his mother as leverage ...
The Last Starfighter (1984)
Video game expert Alex Rogan finds himself transported to another planet after conquering The Last Starfighter video game only to find out it was just a test. He was recruited to join the team of best starfighters to defend their world from the attack.
Many of those details match the 1968 musical Chitty Chitty Bang Bang. It involves a flying car, the father is an inventor who creates a new type of candy, and the children are captured by the evil Child Catcher and imprisoned.
This is actually a commonly occurring plot motif. However, the most explicit example of this would be "The Ones Who Walk Away from Omelas" by Ursula LeGuin (PDF). The titular "ones" are those people who refuse to accept the suffering for one child as a necessity to preserve their utopia.
The only chronological element of the work is that ...
I'm pretty sure this is actually from a book: Douglas Adams's third Hitch-Hiker's book, Life, The Universe and Everything.
Slartibartfast is explaining exactly why the Krikkiters are so traumatised by a spaceship crashing on their planet:
"No," said Slartibartfast, with a slight quickening of his step, "the people of Krikkit have never thought to ...
This is Disney's 1986 film, The Flight of the Navigator
On the night of July 4, 1978, in Fort Lauderdale, Florida, 12-year-old David Freeman walks through the woods to pick up his 8-year-old younger brother, Jeff, from a friend's house when he accidentally falls into a ravine and is knocked unconscious. When he comes to, he discovers that eight years have ...
Rainbow War (1985)
Rainbow War was featured in the Canadian Pacific Pavilion as part of Expo 86 in Vancouver, BC, Canada. It is available on DVD and Blu-ray from Pyramid Media.
A fan site has more information about the film, its cast, and its production history.
Three nations with strong ...
You're describing Logan's Run.
In the year 2274, the remnants of human civilization live in a sealed
city contained beneath a cluster of geodesic domes, a utopia run by a
computer that takes care of all aspects of their life, including
reproduction. The citizens live a hedonistic life but in order to
maintain the population levels everyone must ...
This is the 2001 film A.I. Artificial Intelligence.
The Blue Fairy (not Angel) is a recurrent theme in the movie.
Here is the part about being trapped underwater, from the linked Wikipedia article.
David tells Joe he saw the Blue Fairy underwater and wants to go down
to meet her. Joe is captured by the authorities using an
electromagnet. David and ...
This sounds like the short story "At the Core" by Larry Niven.
Four years after the events in the other short story "Neutron Star", spaceship pilot Beowulf Shaeffer is on Jinx, a planet orbiting Sirius B, when he is again contacted by the Puppeteers, this time by the Regional President of General Products on Jinx, who offers him a chance to guide a ...
I'd suggest that this is likely to be a somewhat poorly-recalled "The Forever War" by Joe Haldeman.
This does feature "time travel" although this is related to the difference in relative speeds for interplanetary travel due to time-dilation.
"Exactly. You've lost about nine years, though, to time dilation, while we maneuvered between collapsar jumps. In ...
This is Neil Stephenson's The Diamond Age.
The protagonist in the story is Nell, a thete (or person without a tribe; equivalent to the lowest working class) living in the Leased Territories, a lowland slum built on the artificial, diamondoid island of New Chusan, located offshore from the mouth of the Yangtze River, northwest of Shanghai. At the age of ...
The story is definitely taken straight from Aldous Huxley's Brave New World.
A "chill pill" called soma
A society with a completely relaxed and open attitude toward sex and intimacy (in the book people refer to it as "enjoying" someone, as in "Have you enjoyed so-and-so lately?")
A method of teaching this behavior to children; the beginning ...
That would be Korgoth of Barbaria, an animated pilot that was not picked up. It aired in the summer of 2006.
Korgoth is infected with a deadly parasite by Gog-Ma-Gogg and extorted to steal an item known as "The Golden Goblin of the Fourth Age" from the wizard Specules, who Gog believes to have recently died. He journeys with a group of ...
This is likely A Canticle for Leibowitz by Walter M. Miller Jr.
After 20th century civilization was destroyed by a global nuclear war, known as the "Flame Deluge", there was a violent backlash against the culture of advanced knowledge and technology that had led to the development of nuclear weapons. During this backlash, called the "Simplification", ...
"The Accomplice" (April 1967), by Vernor Vinge
Originally published in Worlds of If Science Fiction, 1967.
Bob Royce, CEO of Royce Technology, Inc., and his security officer Arnold Su have discovered that one of their employees has embezzled 4 million dollars worth of computer time. The evidence points to Howard Prentice, a 90-...
Assuming you got the number wrong, it's Robert Silverberg's The Man in the Maze:
“The Hydrans,” he said, “have either five sexes or none, I'm not sure which. That's a measure of how well I got to know them while I was there. However they do it, I think people have more fun. Why are you standing over there, Marta?”
The context is that Muller (the main ...
Rogue Moon (1960) by Algis Budrys.
Rogue Moon is largely about the discovery and investigation of a large alien artifact found on the surface of the Moon.
The object eventually kills its explorers in various ways—more specifically, investigators "die in their effort to penetrate an alien-built labyrinth where one wrong turn means ...
You don't specify if this is a book, film, or TV show but this corresponds very well with segment of Douglas Adams Hitchhikers Guide to the Galaxy stories involving the Golgafrincham ArK Fleet which is comprised of "the useless third of the population" When their planet is endangered this portion of the population is put on a spaceship and programmed to ...
This is "A Statue for Father" (1959) by Isaac Asimov.
A theoretical physicist and his son work on the theory of time travel, and experiment with a method of reaching back into time and retrieving objects
More by serendipity than design, they manage to retrieve a nest of dinosaur eggs which in due course hatch.
They keep on working ...
This is Mr. Tompkins in Wonderland (1939). After attending a lecture on relativity the protagonist dreams that he enters a fantastical world where light moves at a mere fraction of the speed of sound.
When he opened his eyes again, he found himself sitting not on a
lecture room bench but on one of the benches installed by the city
for the convenience ...
Terry Brooks's Magic Kingdom for Sale -- Sold.
The novel begins with Ben Holiday, a trial lawyer from Chicago, lamenting the loss of his wife and unborn child in a car accident. He finds an advertisement in an upscale Christmas catalog claiming to offer a magical kingdom for one million dollars by a man named Mr. Meeks. Although skeptical, Ben pursues ...
This is almost certainly the first short story in Frank Herbert's book "The Godmakers"
In the first story, "You Take the High Road" - the protagonist, Lewis Orne, is the agent.
The mentor notes that the suspect culture has the following:
Straight broad roads good only for transporting troops across high ...
It's SF, not fantasy, but monks that do math, alternate "dimensions" (inter-universal travel) and multiple zones sounds a lot like Anathem (2008) by Neal Stephenson. It's definitely a tome; the trade and paperback editions ran over 1000 pages.
The story is set on Arbre where monastery-like places called "concents" are where the thinkers are cloistered.
I would think you are looking for 'The City and the Stars' by Arthur C Clarke
The City and the Stars is a science fiction novel by British writer Arthur C. Clarke, published in 1956. This novel is a complete rewrite of his earlier Against the Fall of Night, which was Clarke's first novel, and was published in Startling Stories magazine ...
This sounds like The Mote in God's Eye by Niven and Pournelle.
The front cover features a quote from Robert Heinlein, "Possibly the finest science fiction novel I have ever read."
It's set in the CoDominium universe after the rise of the Second Empire of Man.
The moties don't arrive by Alderson jump point, they traveled in a solar sail-type craft that had ...
I don't have my copy of Axiomatic on hand to verify, but this sounds a lot like "Learning to Be Me" by Greg Egan.
I was six years old when my parents told me that there was a small, dark jewel inside my skull, learning to me be.
Opening line of "Learning to Be Me"
In the story, everyone has a neural implant called a "jewel" inserted into their brain ...
This could be the 1990s TV show Babylon 5
Spaceship like Star Trek.
LOTS of spaceships
Alien spaceships have 4 legs?
The spaceships of the Shadows (an alien race) kind of have lots of leg-like appendages:
The story is about the fight between the human race with an alien species,The human race is almost annihilated. They lost every fight but keep ...