"Sleeping with the Enemy" is the third episode of the sixteenth season of the American animated television series The Simpsons. It originally aired on the Fox network in the United States on November 21, 2004. In the episode, Marge finds Nelson and acts as a mother figure towards him due to her belief that her children lost interest in her. Meanwhile, Lisa gets teased about her big butt, and becomes obsessed with her weight. To date, this is Jon Vitti's last episode as writer and Lauren MacMullan's last episode as director. Plot Lisa gets teased by Sherri and Terri about her big butt, making her embarrassed and self-conscious about her weight. Homer only makes matters worse when he tells her about the "Simpson butt", something that all Simpsons have. Bart brings home a geography test with a grade of 100, eagerly expecting a party that was promised to him if he had got a 100. Despite Homer discovering that the watermark of Bart's test is real and that all the answers are correct, he and Marge speak to Bart's teacher. Mrs. Krabappel confesses that she did not bother to fold up the map during the test, so Bart and everyone else received 100. Marge throws Bart a party, which is attended by Patty and Selma, Grampa, Grandma, Ralph, and even Martin. Milhouse can only attend via speakerphone because he is sick with measles. Bart hates the party and to make matters worse, Lisa runs up to her room crying when Marge offers her one slice of cake. Marge thinks her children no longer appreciate her, so when she finds Nelson catching tadpoles from a water fountain at the zoo, she decides to become a mother figure by spending quality time with him. They bond as Nelson tells Marge about his poor life involving his father abandoning him and never coming back. Marge brings him home so he can do some chores. Nelson's mother finds this out and does not want Marge giving them any charity. Later that night, Mrs. Muntz leaves town, and Nelson, having nowhere else to go, stays with the Simpsons. Marge lets him sleep in Bart's room, forcing Bart to sleep underneath his bed. Late one night, Bart sees Nelson sing about his missing father, and sees Lisa eat an entire Labor Day cake as she was unable to take any more starvation. As Bart walks away,