After going back-to-school shopping, Homer learns from Apu that he can sell grease to make a profit. At breakfast, Homer begins frying up various amounts of bacon to use the grease to make money and decides to have Bart help him with his "grease business" which forces Bart to quit school. Meanwhile, on the first day back at school, Lisa volunteers to help Alex Whitney, a fashion conscious new student, by showing her around the school. To help her make new friends, Lisa takes Alex, Sherri, Terri, Allison Taylor and Janey for lunch in the cafeteria after the two groups group meet up, but shortly after abandon Lisa after seeing that Alex has adult items like a cell phone, a purse and perfume.
Homer and Bart begin their grease business and make sixty-three cents worth of grease from twenty-seven dollars' worth of bacon, much to Homer's glee and Bart's disappointment. After Bart points out that they need larger amounts of grease, the pair drive to Krusty Burger, where they attempt steal grease from the fryers. After loading it into Marge's car, two employees of The Acne Grease and Shovel Company steal it, claiming they control the grease and shoveling business in the city.
Alex convinces Principal Skinner to have a school-dance rather than the regular yearly event of apple picking. Skinner agrees, so Alex and Lisa, accompanied by Sherri, Terri, Janey and Allison visit the mall to purchase party supplies, but the girls detour and begin trying on outfits for the dance, despite Lisa's protests. The group leave the mall, none speaking to each other. Lisa decides not to attend the dance, but changes her mind and goes to the school to take tickets at the door, but later arrives and discovers the boys and girls are standing on different sides of the room, and explains to Alex that it is like this because they are only children, not adults.
Homer and Bart arrive at the school during the school-dance to steal the grease in the school's kitchen which Bart told him about. They sneak into the kitchen and plants a hose in the fryer to suck it in to the car, but Willie spots them and attempts to stop them, claiming the grease to be his retirement plan. Homer tries to escape, but Willie grabs his legs and strangles him with the hose sucking the grease, which explodes due to the increased pressure, causing the grease to flood into the dance hall. A grease fight begins among the students, where Alex eventually joins in after being told by Lisa to act her own age.