At the Springfield Swap Meet, Bart and Lisa Simpson notice Homer on the cover of an LP album. Homer explains that he, Principal Skinner, Barney, and Apu recorded a barbershop quartet album in 1985, which catapulted them to national fame. He then tells his family the story of how the album came to be. While performing at Moe's Tavern, an agent offered to represent the group as a band, but only on the condition that they expel Chief Wiggum, who was the band's fourth member at the time. After Homer abandons Wiggum in the woods, an audition is held during which the band rejected candidates to fill Wiggum's position, among others Jasper Beardly, Groundskeeper Willie and Wiggum disguised as Doctor Dolittle, the trio returned downheartedly to Moe's Tavern, where they recruited Barney after hearing him sing in a beautiful Irish tenor voice. The four members then brainstormed on a name for the group, eventually settling on The Be Sharps.
In the present, Homer brags that he sold his car's spare tire at the swap meet. On the way home, one of their tires blows out. While Marge walks to a gas station to get a new tire, Homer continues his story. He tells Bart and Lisa that after Marge bought a Baby on board sign, Homer wrote a song inspired by the fad. The song "Baby on Board" appeared on the group's first album, Meet The Be Sharps, and the song became a hit. The Be Sharps performed the song at the Statue of Liberty's centennial in 1986, and they later won a Grammy Award for Outstanding Soul, Spoken Word, or Barbershop Album of the Year for Meet The Be Sharps.
Back in the present, the Simpsons are at home, where Homer explains that The Be Sharps became so popular that they were featured on merchandise, including lunch boxes, mugs, and posters. The band later released their second album, Bigger than Jesus. While The Be Sharps grew in fame, creative disputes arose when Barney dated a Japanese conceptual artist (a parody of Yoko Ono), which eventually led to his leaving the group. Barney and his girlfriend recorded a song in which his girlfriend repeatedly says "Number 8" over tape loops of Barney's belches (a parody of The Beatles' "Revolution 9"). Ultimately, the group realized they were no longer popular. The latest issue of Us Weekly's What's Hot and What's Not confirmed this, noting that the band was no longer "hot". The band then split up; Principal Skinner returned to the Springfield Elementary School, Apu to the Kwik-E-Mart, Barney back to Moe's Tavern, and Homer to the Springfield Nuclear Power Plant, where his position has temporarily been filled by a chicken. Returning to the present day, the group reunites to perform a concert on the roof of Moe's Tavern, singing their number one hit "Baby on Board". Pedestrians stop and listen to them singing their comeback concert, including George Harrison of The Beatles, who dismissively remarks, "It's been done."