On Valentine's Day, Homer and Marge get stuck in a tunnel of love (thanks to Bart and some gelatin), so they pass the time with love stories of three couples, animated for our enjoyment:
Homer and Marge as Bonnie and Clyde,
Homer and Marge (again) as "Shady and the Vamp"
Nelson and Lisa as Sid Vicious and Nancy Spungen.
The episode begins on a Valentine's Day afternoon. As a Valentine's Day treat, Homer takes Marge to a carnival, where they lose the kids in order to spend the day with one another in the Tunnel of Love. Inside, the two enjoy each other's company, however, Bart attempts to spoil his parents' happiness by filling the water with freezing jello, causing Homer and Marge's boat to stop. Trapped, Homer decides to pass time by telling Marge a love story: Bonnie and Clyde.
Bonnie and Clyde
In 1933, during the Great Depression, Bonnie Parker (Marge) rejects a man trying to get her attention (Cletus), saying she is looking for someone exciting. Clyde Barrow (Homer) then arrives, and after robbing a store, the two run off. Clyde discovers Bonnie's passion is violence, and the two go on a crime spree by robbing banks. After tricking a citizen car idiot (Ned Flanders) into helping them, the two garner intense popularity in the country for. The car idiot who was tricked by Bonnie and Clyde soon realizes what had happened, and snitches to the police. The Louisiana officers soon arrive, and the cops gun Bonnie and Clyde down. While dying, Bonnie tells Clyde that she is looking for a man with more excitement.
Shady and the Vamp
Bart and Lisa arrive at Marge and Homer's boat, where Marge launches into a story of two dogs in love, Shady and the Vamp. Vamp (Marge) is a royal and luxurious female dog. Shady (Homer) is in love with Vamp and eyes her from a distance, vowing that he will win her. After he is trampled by a mob of children, Vamp comforts Shady, and he asks her out for dinner. The two go to Luigi's, where, after a romantic pasta dinner, the two run off onto a hill. In the morning, Vamp wakes up with nauseous feelings, and Shady leaves her, knowing she is pregnant. In a musical entitled "Any Minute Now", the two dogs await for the other's return, though the siamesse cats living with Vamp (Patty and Selma) convince her that Shady would never come back. Two of her puppies (who resemble Bart and Lisa) decide to go look for their father, and after being kidnapped by the dog catcher (Willie), Shady arrives to save them. He returns to Vamp, who takes him back and later tells him that there were actually eleven puppies in the litter (so they have nine other kids besides the two puppies that look like Bart and Lisa).
Sid and Nancy
Bart spins into a winding story in the age of Donny and Marie and The Brady Bunch: Sid and Nancy. Nancy Spungen (Lisa), a young model student walks into a rock concert by the Sex Pistols, where she is enamored by the eccentric bassist, Sid Vicious (Nelson). After viewing him throw a student (Martin) into a jukebox, she decides to go after him. A chocolate dealer (Otto, in a parody of a drug dealer) sells her a chocolate bar which she gives to Sid, who soon begins dating her. As shown in a montage, the two begin having their lives spiraled out of control while gaining a chocolate addiction. The police turn up and Nelson begins flushing chocolate down the toilet. Sid soon begins ditching the Pistols, angering lead singer Johnny Rotten (Bart). Sid arrives in the middle of a performance after a major chocolate spree, and knocks into an amplifier which topples over and crushes their drummer, Paul Cook (Dolph). Nancy arrives to defend Sid, and informs the Pistols that Sid doesn't need them, and the two go off trying to sing a soft type of music, performing at CBGB (Comic Book Guy's Bar). When they are kicked out for a terrible performance, the two plan to go back to their addiction, concluding the story. The episode finishes within Bart's story parodying the Garbage scene in Sid and Nancy, but showing Homer as the person dumping the trash as it covers the final scene.