A humanoid alien (R. L. Ryan) lands on Earth and soon discovers he likes to eat Italian people. Detective McSorely (Ron Silver) is an incompetent police officer, and the only one who knows what's going on. The rest of the police force thinks McSorely has gone nuts, while the alien continues eating the Italian population of New York City.
After a foreboding introduction by a wily old gravedigger, a slightly overweight, drunken punker named Gristle stumbles into a spooky cemetery and proceeds to defile all the graves. His fun is interrupted by a UFO that shoots a beam into the ground and awakens an alien skeleton monster.
Brian begins an unwilling symbiotic relationship with a malevolent leech-like brain-eating parasite called "Aylmer". Aylmer secretes a highly addictive, hallucinogenic blue fluid into Brian's brain. In return for a steady supply of the fluid, Brian must seek out human victims for Aylmer, so that he can devour their brains. All the while, though, as Brian adopts a heavily secluded life in his indulgence of Aylmer's fluids, it begins to draw a rift in his relationship with his girlfriend Barbara and brother.
Mike (Michael Shulman) is a young man who feels he does not belong on Earth. He tries to win the heart of his friend Katelyn (Erika Christensen) by helping out with the Halloween Dance, which is sabotaged by his rival, Scott. Upset, Mike sends a message into space asking to be rescued from Earth, unaware that his message has been heard. Soon a diverse range of aliens come to Earth with various offers for Mike, only to find he has changed his mind after Katelyn gives him another chance.
Joanna Eberhart (Nicole Kidman) is a successful reality television executive producer. She is fired after her latest project, a show called I Can Do Better, where spouses choose between each other or prostitutes, results in one of the jilted men going on a shooting spree and attempts to assassinate Joanna, and she has a nervous breakdown. With her husband Walter (Matthew Broderick) and their two children, they move from Manhattan to Stepford, a quiet Connecticut suburb.
Jeff Peters (John Malkovich) is an emotionally repressed scientist who can't stand others because of their intellectual inferiority. He dreams of deep space exploration, which would be difficult because of the lack of human contact for long periods of time. He develops the Ulysses android (which looks exactly like him) for the purpose of space exploration, since an android would not be affected by the isolation.
Two Evil Alien Conquerors are sent to Earth with the order to behead all humans within 48 hours. If they fail, they will be destroyed by Croker, a 100-foot-tall (30 m) giant.
Wayne Grey (Seann William Scott), a fireman trainee practicing in a shack in the desert near Glen Canyon, Arizona, sees a meteor strike his car and land in an underground cavern. College professor Ira Kane (David Duchovny) and his colleague, geology professor Harry Block (Orlando Jones), investigate, taking a sample of strange blue liquid that oozes from it. Ira discovers that it harbors extraterrestrial single-celled nitrogen-based organisms multiplying exponentially, condensing millions of years of evolution within a matter of hours. The next day, they take the science class to survey the meteor site and find it already surrounded by evolved oxygen-converting fungi and alien flatworms. Ira and Harry discover that the cells and organisms reproduce rapidly through mitosis after seeing one of the flatworms they collected in a jar split into another.
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 young alien, Stu, is inside a spacecraft taking an examination in alien abduction. He must snatch a sleeping farmer named Ernie under the watchful eye of his impassive examiner, a gelatinous blob named Mr. B. Working from memory, Stu is expected to use an array of thousands of identical unlabeled toggle switches for this purpose and Mr. B gives no hints of which one(s) to use.
A college professor is working on a long-term scientific experiment when a baseball comes through the window, destroying all of his glassware and spilling the fluids that the flasks and test tubes contained. The pooled fluids combine to form the (fictitious) chemical "methylethylpropylbutyl," which then covers a large portion of the baseball. The professor soon discovers that the fluid, along with any object with which it makes contact, is repelled by wood (cf. Alexander Fleming's serendipitous discovery of penicillin).
In the Kingdom of Oriana, Princess Oriana, ruler of the kingdom, has been informed by a local fortune teller Pearl that her evil uncle, the Duke of Zill, is invading the kingdom. To counter the threat of the Duke, Oriana and Pearl descend into the cavern underneath the castle and attempt to use an ancient device called the "Dimensporter" in order to escape to another dimension and find a hero to save the kingdom. However, they are caught by the Duke's robotic army and imprisoned, while the Duke himself seizes control of the kingdom. As the princess is taken away by the Duke's "Cylinder" robots, she sheds a magical tear, which flies into the Dimensporter in her place and is transported to Felix's dimension, where the eponymous feline is taking a nap underneath a palm tree when the tear finds him. The tear wakes and guides him to an abandoned gold mine, where the Dimensporter is located. Felix, with his magical bag of tricks, is soon transported to the Kingdom of Oriana.
Distinguished Professor Gordon (John Hoyt) explains that Earth is being tormented by periodic "sex rays" which send people into a sexual frenzy. When one of the rays hits the Ford Tri-Motor passenger aircraft carrying Flesh Gordon (Jason Williams) and Dale Ardor (Suzanne Fields), the pilots abandon the controls and everyone aboard has manic sex. When they finish, Flesh and Dale escape the imminent crash by parachute. They land near the workshop of Flexi Jerkoff (Joseph Hudgins), who has a plan to stop the sex rays at their source.
Joe's accidental snapshot of a paper plate blown by a breeze, is mistaken for a picture of a UFO. However, Moe and Larry take the credit for the photo, and are paid a huge sum. Angered, Joe leaves the boys for a camping trip, only to meet two genuine and beautiful aliens from Planet Zircon who allow Joe to photograph them. Moe and Larry end up arrested when their UFO picture is revealed to be a fraud. They are put in straitjackets and incarcerated in a psychiatric hospital while Joe becomes a national hero.
The film begins on "Friday, April 17" at 4 pm in Venice, California. Huckleberry P. Jones (Gene Cunningham), local pimp, narcotics peddler and slumlord, enters a vacant house that he owns. While stashing heroin in the basement, he stumbles upon a mysterious door and enters it, falling into the Sixth Dimension, from which he promptly escapes. After retrieving the heroin, he sells the house to the Hercules family. On their way to school, Frenchy Hercules (Marie-Pascale Elfman) and her brother Flash (Phil Gordon) have a conversation with Squeezit Henderson (Matthew Bright), who tells them that, while being violently beaten by his mother, he had a vision of his transgender sister René (also played by Bright), who had fallen into the Sixth Dimension through the door in the Hercules' basement. Frenchy returns home to confide in her mother, and decides to take just a "little peek" behind the forbidden door in the basement. After arriving in the Sixth Dimension, she is captured by the perpetually topless Princess, who brings Frenchy to the rulers of the Sixth Dimension, the midget King Fausto (Hervé Villechaize) and his queen, Doris (Susan Tyrrell). When the king falls for Frenchy, Queen Doris orders their frog servant, Bust Rod, to lock her up. In order to make sure that Frenchy is not harmed, King Fausto tells Bust Rod to take Frenchy to Cell 63, where the king keeps his favorite concubines (as well as René). The next day at school, Flash tries to convince Squeezit to help him rescue René and Frenchy. When Squeezit refuses, Flash enlists the help of Gramps instead. In the Sixth Dimension, they speak to an old Jewish man who tells them how to help Frenchy escape, but they soon are captured by Bust Rod. Queen Doris interrogates Flash and Gramps and then lowers them into a large septic tank. She then plots her revenge against Frenchy, relocating all the denizens of Cell 63 to a torture chamber. She leaves the Princess to oversee Frenchy's torture and execution, but when a fuse is blown, the torture is put on hold and the prisoners from cell 63 are relocated to keep the King from finding them.