"New Kids on the Blecch" is the fourteenth episode of Season 12.
When a music producer discovers the musical abilities of Bart, Nelson, Milhouse and Ralph, it scurries to set them up as the next big boy band sensation, complete with a sinister subliminal propaganda campaign in mind: "Join the Navy" disguised as "Yvan eht Nioj".
Homer joins the Springfield Marathon, along with other Springfieldians, including Mr. Burns and Smithers and Comic Book Guy (dressed as The Flash). By paralleling Rosie Ruiz's cheating in the 1980 Boston Marathon, Bart who disguises himself as Italian wins the Springfield's equivalent. When it is discovered Bart cheated, he finds himself in hot water with fellow competitors and spectators, so he accepts a stranger's offer to help him escape. The stranger reveals that his identity is L.T. Smash. L.T. offers Bart a job in a boy band known as "Party Posse". Bart accepts, and becomes Party Posse's fourth member, Caly, joining Krit (Nelson Muntz), P.G. (Ralph Wiggum), and Wowz (Milhouse Van Houten), boys from Bart's school.
Party Posse quickly ascend to stardom, albeit using complex voice enhancers built by NASA. No one is aware of the voice enhancer's use, and as such Party Posse's success depends on the voice enhancer. The band releases a single titled Drop Da Bomb, which contains a suspicious lyric; Yvan Eht Nioj. Lisa's growing suspicion around Party Posse eventually results in her discovering the line is a subliminal recruiting message to join the Navy, as Yvan Eht Nioj is Join the Navy written backwards (see Friend With a Benefit, season 27). Lisa also discovers that L.T. Smash is, in reality, a lieutenant (named Lieutenant L.T. Smash), who is working for the government to recruit people for the navy.
Lisa points out her discoveries to Homer and Marge, but they dismiss her accusations as jealousy to Bart. When The Party Posse perform a concert on an aircraft carrier, Lisa's suspicions are increased. During the concert, L.T Smash is alerted by his superior officer that Mad Magazine's next issue will have The Party Posse on the cover, being lampooned as "The Potty Posse."
Smash's superior officer attempts to shut down "Project Boy Band" by cutting off the band's voice enhancer, but Smash refuses and starts to go insane. Smash soon carries the boat off the carrier, heading towards New York City.
N'Sync arrives and attempts to stop Smash before he reaches New York, but the band's attempt fails. Smash fires missiles at Mad Headquarters, destroying the offices, but the workers manage to survive. Smash is soon arrested, and The Party Posse, disappointed that they did not appear on the cover of Mad, decide to divorce.
N'Sync appears at the end of the episode and explains how the Navy protects Americans each and every day, and reveal that the band got JC Chasez enlisted in the Navy. Chasez is soon dragged away by two Military Police officers.