The space armada from Mars, known as the Imperial Atomic Space Navy (Battle Group Seven), fights an interstellar war against their long-time enemy, the Arcturans. The armada is forced into battle by Enforcer Droids, tasked to keep the Martian soldiers in line, despite objections by some that it won't work. Meanwhile, an incompetent crew of a small Martian spaceship, from the Civilian Asteroid Patrol, intercept a distress signal from the fleet, followed by a Halloween rebroadcast of Orson Welles' 1938 The War of the Worlds radio dramatization.
The Earth is passing through the tail of a comet, an event which has not occurred in 65 million years, the last time coinciding with the extinction event that wiped out the dinosaurs. On the night of the comet's passage (which takes place eleven days before Christmas), large crowds gather outside to watch and celebrate.
The movie opens with the invisible Nick Halloway (Chevy Chase) dictating his memoirs into a video camera. To prove it is not a camera trick, he chews some bubble gum. Nick goes on to narrate the story of how he came to be invisible, beginning a few days earlier at his job as a stock analyst. His secretary, Cathy DiTolla (Rosalind Chao), refers to him as a "bullshit artist", and he spends most of his life avoiding responsibility and connections with other people. At his favorite bar, the Academy Club, his friend George Talbot (Michael McKean) invites him to join his table where Nick meets Alice Monroe (Daryl Hannah), a TV documentary producer. Sharing an instant attraction, Nick and Alice make out in the ladies' room. When Alice has to leave, Nick drinks heavily to console himself, although the pair set a lunch date for Friday.
The film takes place in a distant future where water is so scarce and rationed that it is considered an immensely valuable substance, both as a commodity and as a currency in ice cubes. The Templars of Mithra control the water and they destroyed worlds that had natural water leaving the galaxy virtually dry. Pirates dedicate their lives to raiding ships and looting the ice from the cargo holds to make a living. Jason (Robert Urich) is the leader of a band of pirates that raided a Templar cruiser for its ice, and discovered a beautiful princess (Mary Crosby) in a stasis pod. He decided to kidnap her, waking her up, and alarming the Templars. Jason and his pirates fled, but were pursued by Templar ships. Jason let some of his crew, Maida (Anjelica Huston) and Zeno (Ron Perlman), escape while Roscoe (Michael D. Roberts) stayed to help Jason. They were captured. During their capture, they met Killjoy (John Matuszak) who's been pretending to be monk to avoid being a slave. Jason and Roscoe are sentenced to become slaves, a process which includes castration. Roscoe and Jason are spared castration by the princess, who has taken an interest in them. Princess Karina purchased them as her slaves, to work as servants during her party. That evening, they were reunited with Killjoy (disguised as a robot). Jason, Karina, Roscoe, Killjoy and Nanny managed to leave the planet before the Supreme Commander (John Carradine) arrived to arrest her. Princess Karina is spoiled, and she hired Jason so she can find her father, who went missing while searching for a planet with water. It is rumored he discovered one and the Templars would do anything to keep it a secret in order to maintain power. On their next planet, Jason and Roscoe got reunited with their fellow pirates, Maida and Zeno. They proceed to locate the "lost" planet that contains massive amounts of water. The planet must be approached on a specific course or the ship will be suspended in time forever. The course apparently contains some sort of real or illusory time distortion (resulting in both the heroes and the villains reaching old age during the climactic battle). In the end, the day is saved by the now-adult son of Karina and Jason, the result of a romantic tryst just before entering the time distortion field. As the heroes exit the field, everyones ages regress to what they originally were, leaving Jason and Karin with the knowledge that they will have a child together.
A denizen (Garry Shandling) of a faraway planet occupied only by highly evolved males is ordered by his superior, Graydon (Ben Kingsley), to find a female human, impregnate her and bring the baby back to the planet.
Celeste (Kim Basinger) is an alien sent on a secret mission to Earth and Steven Mills (Dan Aykroyd) is a widowed scientist who is working on different ways to send radio waves into deep space. An accident causes a disruption of gravity on Celeste's home world (Cosine N to the 8th). She's sent to investigate who could affect gravity and how it was done, believing it was an attack. She's aided by an alien device resembling a tentacle with an eye, which hides in a designer purse to aid Celeste with her encounters on Earth. The Bag is able to create any object, such as diamonds and designer dresses almost instantaneously. Celeste crashes a party hosted by Steven's brother Ron (Jon Lovitz) where she immediately draws attention to herself by making dated references to old TV shows and political slogans under the mistaken belief that it was current (her superiors had just collected the information, which had taken 92 years to get from Earth to her home world).
On Life Day, Chewbacca, accompanied by Han Solo, is headed home to see his family. Along the way, the duo are chased by two Star Destroyers, but they escape into hyperspace.
A group of CIA officers watch a video presentation of a top-secret project called "Crossbow": a space shuttle mounted with a computer-guided laser weapon incinerates a man on the ground with pinpoint accuracy. Researchers on the project have yet to devise a system to generate enough power to operate it. When it becomes clear that this weapon has no wartime applications and is intended solely for illegal assassinations, one agent decries the project as immoral. He is subsequently eliminated.
Dr. Michael Hfuhruhurr (Steve Martin), a widowed brain surgeon, is renowned for inventing a method of "cranial screw-top" brain surgery. He saves the life of Dolores Benedict (Kathleen Turner), a gold-digging femme fatale who is accidentally run over by Hfuhruhurr when fleeing the scene of her latest husband's fatal coronary (which her malicious mind-games and scheming caused).
The film opens in 2018 with an American manned landing mission to the Moon. The lander carries two astronauts, one of them an African American male model, James Washington, specifically chosen to aid the U.S. President in her re-election (various "Black to the Moon" word-play posters are seen in the film, extolling the new Moon landing).
Helm is sent to the ICE (Intelligence and Counter Espionage) Training Headquarters to uncover a traitor in the organisation. Whilst there he meets ICE agent Sheila Sommers, the pilot of the saucer who has been recovered from a Central American jungle with no memory of what happened to the saucer she flew. Due to the electo-magnetic power of the saucer, only a woman is able to fly it, males of the species are killed by the energy.
Sam Lowry (Jonathan Pryce) is a low-level government employee who has frequent daydreams of saving a damsel in distress. One day he is assigned the task of trying to rectify an error caused by a fly getting jammed in a printer, misprinting a file it was copying, resulting in the incarceration and accidental death during interrogation of cobbler Archibald Buttle, instead of the suspected terrorist, freelance heating engineer Archibald Tuttle.
Ben Crandall (Ethan Hawke) experiences vivid dreams about flying through clouds and over a vast, city-like circuit board...usually after falling asleep watching old sci-fi movies (War of the Worlds is a favorite). Every night, upon waking from the dream, he draws the circuit board. Ben shows the sketches to his friend Wolfgang Muller (River Phoenix), a child prodigy. At school, Ben develops a crush on Lori Swenson (Amanda Peterson) - but he isn't sure whether it's mutual. Both boys meet punkish-but-likeable Darren Woods (Jason Presson), with whom they share their circuit board-concepts. Wolfgang builds an actual microchip based on Ben's drawings. The chip enables the generation of an electromagnetic bubble which surrounds a pre-determined area. As the boys discover, said bubble is capable of moving at near-limitless distances and speeds without the usual ill-effects from inertia. They construct a rudimentary spacecraft out of an abandoned tilt-a-whirl seat; they name their ship the Thunder Road, after Bruce Springsteen's song of the same title. Their experiments with the Thunder Road draw attention from the US Government, which sends agents to scout the area for unidentified flying objects.
A news report is broadcast informing the world that a mission to stop an incoming asteroid from destroying life on earth has failed and that it will make impact in three weeks time. Dodge Petersen (Steve Carell) and his wife Linda (Nancy Carell) listen to the broadcast from the side of the road. After Dodge has an uninterested response, Linda looks at him in abject disgust and flees the vehicle without saying a word.
Jefferson Reed (Robert Townsend) is a mild mannered school teacher in Washington D.C. His neighborhood is terrorized by a local gang called The Golden Lords led by Simon Caine (Roy Fegan) and allied with drug lord Anthony Byers (Frank Gorshin). One night, Jeff steps in to rescue a woman from the gang only to end up running from them himself. Hiding in a garbage dumpster, he manages to escape. As he climbs out, he is struck down by a glowing green meteorite. His spine is crushed and he receives severe burns. A small fragment of the meteor was left over and taken by a mute vagrant named Marvin (Bill Cosby). Reed awakens several days later in the hospital, but when his bandages are taken off, he is miraculously healed of all injuries.