Marge learns that her aunt Gladys has died and that the funeral will be held on the day the family plans to go to fun-filled Duff Gardens. The trip is postponed. Following the service, Lionel Hutz shows a videotape of Aunt Gladys's will. Included in the will are Patty and Selma, whom Aunt Gladys tells to have children so that they will not spend the rest of their lives alone.

Selma decides she wants to have a baby and searches for a half-way decent man to date, but the best she can do is Hans Moleman, whom she decides to be too ugly to be the father of her children. As a last resort, she considers a sperm bank. When Homer wakes up sick on the day the family is scheduled to go to Duff Gardens Marge asks Selma to take the kids to Duff Gardens while she takes care of Homer at home, hoping to give Selma a taste of motherhood.

Bart and Lisa wear Selma out. Bart gets trapped on a roller coaster, while Lisa drinks the water in the "Little Land of Duff" boat ride and hallucinates. The day turns into Selma's worst nightmare. Happy to gate Bart and Lisa home, she decides that kids are too much for her to handle. Instead she happily adopts Jub-Jub, Aunt Gladys's pet iguana.