Milhouse Doesn't Live Here Anymore is the twelfth episode of Season 15.
Milhouse moves away from Springfield and Bart realizes just how much he meant to him. After a bout of sadness Bart finds friendship with an unlikely source: Lisa.
During a school field trip, Bart notices a change in Milhouse's behavior as he calls Krabappel "crab-Apple" which really pleases Jimbo, Dolf and Kearney. Milhouse talks back to Mrs. Krabappel, wanders away from the group and causes mischief with Bart, and tells Bart he doesn't care what anyone thinks of him anymore. Finally, Milhouse reveals that he is moving to Capital City with his mother.
Bart visits Milhouse in Capital City, only to find that Milhouse has dyed his hair blond, is wearing fashionable clothes, and is cultivating a "bad-boy" image, even going so far as to give Bart a wedgie in front of his new Capital City friends. At home, seeing how depressed Bart is, Marge suggests he spend more time with Lisa. The two begin to bond by washing the car and riding bikes, and after they discover an Indian burial mound together, they become best friends.
Milhouse returns to Springfield when his father wins custody of Milhouse via court order. After she finds out Bart told Milhouse about their secret Indian burial mound, Lisa feels that Bart is acting like their friendship never existed and that he has been using her to fill a void. Bart, however, shows her that he still values her as a sister by giving her a set of cards with nice things he will do for her on them, and the two hug.
At Moe's Tavern, Apu and Manjula are celebrating their anniversary, and Homer realizes he does not have anything for Marge for their anniversary. After being thrown out of the bar, Homer sits on the street and people give him money. He dances and earns enough money to buy Marge some flowers.
Homer continues his panhandling, and eventually makes enough money to buy Marge a pair of diamond earrings. When he continues panhandling afterward, angry bums bring Marge to see what Homer is doing. Marge is mortified and offened, but is unable bring herself to place the earrings in the trash.
The episode finishes with Isabel Sanford at the TV and Radio museum, pointing out how sitcoms usually resort to using sappy endings for their episodes, and finally begging George Jefferson to come back.