Selma decides to test her maternal instincts before having kids of her own by taking Bart and Lisa to Duff Gardens to try out her parenting skills.
After Great Aunt Gladys dies, the Simpsons attend the funeral and subsequent reading of the will. On the video will, Great Aunt Gladys warns Patty and Selma not to die alone without a husband and children as she did. Selma starts to worry that her biological clock may be ticking, and decides to find a way to become pregnant. Selma tries video dating and eventually considers an anonymous sperm donor.
Meanwhile, Homer promises Bart and Lisa that they will go to Duff Gardens, a popular amusement park, but Homer becomes ill after eating a spoiled sandwich. Marge, in an effort to give Selma a chance to experience the responsibilities of parenthood, nominates her to take the two. Bart and Lisa wear Selma out at Duff Gardens. Lisa hallucinates after drinking some "water" in The Little Land of Duff and Bart is detained by park security after pant sing a George Washington robot, apparently causing it to malfunction, and faking his height to go on a ride he is not tall enough for and needing rescue. After these negative experiences caring for Bart and Lisa for a day, Selma decides she can live without children, and adopts Jub-Jub, Gladys's iguana, instead (until "Goo Goo Gai Pan", when she adopts Ling Bouvier, but still keeps Jub-Jub too).