Principal Skinner introduces Bart and his classmates to their new gym teacher, Coach Krupt. Krupt revels in hurling balls at the students, inflicting great pain on all of them. The next morning during breakfast, a shell-shocked Bart tells Marge that the teacher is bullying him. Homer enters the kitchen holding a pair of ripped blue pants. Homer tries to find a new pair at “fat man’s stores,” but he’s told they’re no longer manufactured. Meanwhile, at school, Bart finds the coach’s lesson plans, and realizes that Krupt intends to continue his bombardment exercises for months. Seeking revenge, Bart fills a gym ball with water, and then freezes it. During the next gym class, a deranged-looking Bart throws the icy gym ball at Krupt. Krupt ducks, and the ball sails out a window, demolishing Willie’s old shack. Bart apologizes to Willie for the mishap. When Marge stops by the school, she notices Willie sitting in the ruins of his shack. She invites him to spend the night at the house. Willie is touched, and gives Marge a sculpture made out of lost retainers as a token of his appreciation. It doesn’t take long for Lisa to notice that Willie seems resigned to living in poverty. To the strains of “Wouldn’t It Be Loverly” from My Fair Lady, Willie imagines what life would be like if he improved his living conditions. Lisa decides to turn Willie into a “proper gentleman” for her upcoming school science fair. Bart bets Lisa she’ll never pull it off.

Lisa tells Willie she’ll be giving him lessons in “poise, pronunciation, and posture.” Inside a pants factory, a man named Eli Stern tells Homer that he’ll begin manufacturing his favorite pants again if Homer can generate interest from the public. Homer believes that what he needs is a really catchy advertising campaign. At Willie’s shack Lisa continues her etiquette lessons. Willie is haunted by his father, who used to tell him he’d never amount to anything. Back at home Marge reacts with shock and concern when she sees the words “Buy Blue Pants” painted on Homer’s skull. Homer calls it “headvertising,” which “creates brand awareness without relying on traditional media.” As time passes Lisa begins to fear she won’t be able to change Willie in time for the science fair. Willie pulls himself together, and begins to speak elegantly, like actor David Niven. Later, as the science fair gets underway, Willie is introduced to the crowd as “G.K. Willington.” Lisa did such a good job coaching Willie that no one recognizes him. Willie is a smash. He dances with Mrs. Krabappel and other women attending the science fair. It comes time for Principal Skinner to announce the winner of the competition. Before he does so, he makes note of the fact that Lisa didn’t submit an entry. Lisa informs Skinner that she did enter a project: Groundskeeper Willie. With that, Willie rips off his pants, revealing a kilt beneath.

Lisa wins first place at the science fair. Willie shows up at the house, wondering when their next lesson will begin. Lisa tells him there won’t be any more lessons, and he’s free to do whatever he’d like. Willie doesn’t know what to do with his life, as he’s always been a groundskeeper. Lisa helps Willie get a job as a maitre d’ at a fancy restaurant, The Gilded Truffle. Unfortunately the clientele treat him like dirt. Homer tells Marge the “headvertising” idea was a terrific success, and now everyone is wearing blue pants. Marge is shocked to discover that Homer’s entire body is now covered with advertising slogans. Homer says he’ll now earn $100 a week with the ads. At the restaurant Willie tells Lisa he misses his old shack. When Krusty treats Willie poorly, Willie loses his temper and bangs Krusty’s head onto the dessert tray. Later Willie returns to the school, where Skinner and the students welcome him.