A family's new satellite TV system starts receiving signals from another planet, and soon it becomes the passageway to an alien world.
Stan installs satellite TV for his family, but, soon, he picks up a signal from another planet and his television system becomes the gateway between the 2. A creature comes to his apartment and only their son Sherman sees it, but his parents don't believe the boy.
A civilization on a distant planet has found a way to solve its garbage problem: by turning it into energy source, and beaming it into outer space. A flaw in the system's found when the signal is accidentally picked up on Earth by the Putterman family's home satellite dish. While this would ordinarily be just another mess, this particular transmission contains a hungry trash monster who quickly begins snacking on the Puttermans and their guests. Only young Sherman has any clue what's going on, but nobody will believe him. Is there any hope for the Earth?
- In the opening scene, a mutant creature disposal unit on the Planet Pluton has gone haywire, sending toxic electrical energy to Earth.
In a suburban neighborhood, shrew housewife Raquel Putterman (Mary Woronov) and her 16-year-old punk teenage daughter, Suzy (Diane Franklin), blame husband and father, Stan Putterman (Gerrit Graham), for breaking their televisions when he installs a new satellite dish, but the technology failure has nothing to do with him. Stan asks Norton (Sonny Carl Davis), the satellite dish representative, to fix his problem, but Norton claims the service contract only allows him to help with repairs not installation. In his frustration, Stan damages the dish with a hammer to create the need for repair. However, a bolt of lightning hits the satellite receiver, and the television sets are back in service.
As Stan demonstrates the wide range of channels, he and his father-in-law, "Grampa," (Bert Remsen) fight over the remote control. As they break the unit, part of the satellite equipment on the patio overheats and melts. In the Putterman living room, the screen shifts from static to a program titled "Medusa's Midnight Horrorthon". Grampa and his 13-year-old grandson, Sherman Putterman (Chad Allen), are engrossed as prehistoric dinosaurs battle each other.
Suzy goes on a date with "OD," (Jonathan Gries) her punk leather boyfriend, while Stan and Raquel spend the night on the lookout for swinger couples with whom to have sex. Grampa and Sherman stare at a round, gelatinous monster on television, but the channel spontaneously reverts to "Medusa's Midnight Horrorthon" and they fall asleep in front of the television. Later, the monster leaps out of the television and scares Grampa and Sherman. When Sherman claims he saw a monster, Grampa retorts that monsters do not exist, and he insists that Sherman saw a burglar.
Grampa locks his grandson in the family's bomb shelter, arms himself with rifles, and instructs Sherman on which weapons to use. Grampa questions Norton when he arrives to fix the satellite dish. The repairman has no knowledge of any burglars but notices that the wiring from the satellite box is spilling out like spaghetti. As Grampa searches the house, Sherman hears a scream from the patio. Norton, the repairman, becomes the monster's first victim. Grampa comes face to face with the monster on the television screen, but is not fazed. The monster squeezes Grampa's head. As brain juice and blood matter spill to the floor, the monster devours Grampa and his clothing.
When Sherman sees the monster convert to electromagnetic waves and disappear into the television screen, he locks himself in the bomb shelter and calls police. Officer Nutky (Ian Patrick Williams) believes Sherman's call is a prank, and ignores him. Sherman tries to warn his parents when they bring home another swinging couple couple named Cherry (Randi Brooks) and Spiro (Alejandro Rey). Raquel notices a puddle of blood and brain matter on the floor. Sherman claims that the puddle is all that remains of Grampa, but she demands her son stop telling stories. Stan gives Cherry and Spiro a tour of the house, and shows off the bedroom hot tub. He fiddles with the satellite channels, and ignores a warning from Pluthar (William Paulson), a planet Pluton sanitation captain, of danger that can only be stopped if Earthlings destroy their televisions and other electronic devices.
In the bomb shelter, the monster emerges from the TV set and transforms into Grampa. Through the shelter door, Grampa tells Raquel Putterman that everything is fine. Sherman, however, insists that Grampa is dead. Raquel locks her son in the shelter, despite his pleas. Sherman grabs his loaded rifle and searches for his grandfather, but the monster has departed back into the TV screen.
Raquel returns to the bedroom, and suggests that Spiro help mix cocktails. Cherry has a bathing suit underneath her dress, and tries out the hot tub while Stan changes into a swimsuit.
Sherman listens as Pluthar issues a second warning over the shelter television set. The alien claims that an accident occurred at the mutant disposal unit that could result in the annihilation of Earth should the monster gain access to any TV station. Sherman panics and calls the "Medusa's Midnight Horrorthon" studio phone number, but Medusa (Jennifer Richards) does not believe his monster story and hangs up.
Meanwhile, Raquel discovers that Spiro is interested in homosexual sex with Stan. When Spiro brings Cherry her drink, Raquel breaks the news to Stan. Spiro joins Cherry in the hot tub, but as he approaches her, two monster arms pull him underwater. When Stan and Raquel return to their guests, they are missing. The monster rises out of the murky water, attacks Stan, and Raquel screams. Sherman hears his parents scream, but when the police ignore his second call for help, he uses explosives to blow open the bomb shelter door.
A few minutes later, Suzy and OD return home, but do not believe Sherman's rantings about the monster. They make their way to their parents' bedroom. Suzy discovers her parents, their guests, and Grampa in bed together (the monster is using their corpses to impersonate them). They claim to be having fun, and shoo her away.
Back in the living room, the monster emerges from the TV set and chases after OD, but decides not to attack because OD's black leather-spiked arm wear, which OD used to shield himself, reminds it of someone important from its childhood. OD offers the monster a snack, and soon, Suzy, Sherman, and OD are teaching the creature English and emptying the refrigerator to satisfy its appetite. They introduce the monster to American rock and roll, and OD plays a cassette tape of his heavy metal band. After the monster learns their names, they teach it about technology. Suzy decides they can promote the creature and make money. Suzy, OD and Sherman agree to be equal partners in the venture. They want their monster to be on television, and call Medusa for help. They invite her to party with the creature, but it is unclear whether she will come or not.
Officer Nutky arrives with a warrant for Sherman's arrest. The monster becomes agitated when Pluthar, the Pluton sanitation captain, appears on TV again for the third time and delivers his warning on the screen. This sets the monster off again and it grabs OD by the face with a monster within the monster's mouth and eats him alive. Officer Nutky announces to Sherman that he's under arrest for making prank phone calls to the station, but Sherman and Suzy escape and hide in the bomb shelter. The monster confronts the policeman, who opens fire on it with his pistol. Unaffected by the bullets, the monster grabs the officer's gun, then devours him as well.
After Suzy finds what's left of OD in the living room, Sherman remarks that they have no choice but to kill it. The monster almost approaches Suzy but Sherman blasts the TV to pieces before the monster can appear. They stock up on weapons and search each room of the house for the creature. When Suzy and Sherman return to their parents bedroom, they find the monster has eaten the adults leaving just puddles of blood and slime on the floor and scraps on the bed. Sherman and Suzy then set about smashing every TV set in the house.
Sherman and Suzy find the monster back in the living room watching the TV set. Sherman sneaks up on the monster from behind, but slips on the creature's trailing slime. The monster grabs him by the leg with one of its tentacles, but Sherman uses his knife to free himself.
A little later in the living room, Pluthar appears in a spacesuit out of the TV set, and announces that he has come to rescue Sherman and Suzy. He explains that, on his planet, "hungry beasts" are pets like dogs and cats, but when they mutate they become unstable and must be destroyed. The monster is a hungry beast that mutated and was accidentally sent to Earth instead of being exterminated.
Medusa arrives at the house where she lets herself in and mistakenly believes Pluthar is about to hurt Sherman and Suzy. She approaches Pluthar, and damages his space helmet by cracking his helmet, which kills him. The monster then blasts through a wall and Suzy screams. Sherman fires Pluthar's rifle but misses, and then the rifle jams. Sherman, wearing OD's arm spikes and holding his arms in a similar position to OD, is sucked into the monster's mouth, disillusioned into believing the monster will have another change of heart. It then cuts to black.
In the morning, the monster, having presumably eaten Sherman and Suzy and Medusa, is now part-Medusa. Climbing into Medusa's limousine, the new hybrid monster orders the chauffeur to drive to the television studio... implying that it will eat the TV staff and use the technology of the TV station and satellite dishes to spread its image all around the world. With no one to stop the monster now, planet Earth is apparently doomed.