During a trip to the swap meet, Bart and Lisa stumble on a record with Homer's picture on it. This prompt Homer to tell the story of when he was in a barbershop quartet.
The original foursome was Homer, Principal Skinner, Apu, and Chief Wiggum. As they start to get popular, they attract the attention of a record producer who wants them to get rid of Wiggum. They do and replace him with Barney and become the B Sharps. Homer writes their first hit, "Baby on Board" based on the yellow signs people used to hang in their cars. They achieve world-wide fame and even win a Grammy. The touring puts a strain on Homer and his family and Barney starts dressing and acting like John Lennon did towards the end of The Beatles run, even dating a Japanese conceptual artists a la Yoko Ono.
Struggling to write more hits, the B Sharps break up and go their separate ways. After he finishes telling the story, Homer calls the guys up. They reunite and sing on the Moe's Tavern rooftop, again like The Beatles.