The Simpson family get a nanny after Marge starts losing her hair to stress.
Marge is treated like a slave by her husband and children, who blatantly refuse to do anything for themselves to the point that they won't get up to get themselves drinks (Bart even makes rasping sounds to guilt Marge into getting it for him).
Soon Marge's hair starts to fall out, and Dr. Hibbert can't figure out what's wrong, that is until a call to the doctor's office by Bart and Lisa (who still refuses to lift a finger), asking their mother to get them glasses of milk despite being across town makes another clump of hair fall out, causing the doctor to realize the hair loss is from stress. Then, the family hires a nanny to help out at the house. Homer attacks all the applicants since he thinks they're all men in drag, like in Mrs. Doubtfire. A nanny named Shary Bobbins (parody of the fictional nanny Mary Poppins), flies out of the sky with her umbrella, lands at their house and applies for the job.
She then helps the children with chores and looks after them while she sings songs to them. She even meets her former fiance, Groundskeeper Willie. Once the family starts to behave properly, she leaves, but the family immediately become dysfunctional again, prompting her to return. After a while, she discovers how lazy and useless they are and gets upset. The family explains, in song, that she can't change them and they're happy just the way they are. As she flies off, Lisa wonders if they'll ever see her again. Homer assures her that they will. Up in the sky, Shary has just been sucked in the jet engine of a plane, then is shredded into pieces, which the family are unaware of.
This is a pun of the song "Supercalifragilisticexpialidocious" from the film Mary Poppins.