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 twin 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.After escaping the septic tank, Flash and Gramps come across a woman who tells them that she was once happily married to the king, until Doris stole the throne by seducing her, "even though she's not my type". The ex-queen has been sitting in her cell for 1,000 years, and has been writing a screenplay in order to keep her sanity.Meanwhile, Pa Hercules is blasted through the stratosphere by an explosion caused by improperly extinguishing his cigarette in a vat of highly flammable tar during his work break at the La Brea Tar Pit Factory. After re-entry, Pa falls through the Hercules family basement and into the Sixth Dimension, where he is imprisoned. Finding a phone, Flash calls Squeezit at his house and again asks for his help. Finally, Squeezit agrees to go into the Sixth Dimension to help rescue Frenchy and René (mostly in order to escape from his abusive mother when he catches her in the arms of a drunken sailor (Joe Spinell)... who happens to be his estranged father). Once in the Sixth Dimension, Squeezit is quickly captured by Satan (Danny Elfman) and his robed minions, with whom he makes a deal to bring him the Princess in exchange for Satan's help freeing René and Frenchy.After Squeezit accomplishes this task, Satan tells him not to worry about his friends before having him decapitated. Queen Doris sends Bust Rod to keep an eye on the king, and to ensure he doesn't find out where she's hidden Frenchy. King Fausto catches Bust Rod and forces him to lead him to Frenchy and René, whom he orders to leave the Sixth Dimension to avoid the Queen's wrath. However, en route to safety, René is stricken with pseudo-menstrual cramps, and they are again captured by the frog.Squeezit's severed head, which has now sprouted chicken wings, finds the king and informs him of what has happened. While preparing to kill Frenchy, Doris is confronted by the ex-queen, and the two engage in a cat-fight, with Doris eventually coming out as the victor. Just as she is about to kill Frenchy, King Fausto stops her, explaining that Satan's Mystic Knights of the Oingo Boingo are holding the Princess hostage, and will kill her should anything befall Frenchy. Flash and Gramps arrive, and Flash is knocked down by Gramps. Ma Hercules enters and, seeing a seemingly dead Flash, shoots Queen Doris. King Fausto mourns Doris, then marries Frenchy to make her his next queen.The film ends with another musical number showing the surviving characters looking toward a great future as they plan to take over everyone and everything in the Galaxy.