Confronted by his own mortality, Grampa decides to give his relatives their inheritance before he passes away. Homer takes Grampa and the family shopping at the mall to buy gifts for themselves. Lisa purchases a talking Malibu Stacy doll, but discovers that the doll can only utter vacuous phrases that reinforce sexist stereotypes.

Marge takes Lisa to the factory where Malibu Stacy is manufactured, but Lisa's complaints receive the standard corporate response. With Smithers's help, Lisa tracks down Stacy Lovell, Malibu Stacy's reclusive inventor. Meanwhile, Grampa, feeling useless and tired of complaining about life, takes a job at the local Krustyburger.

Lisa convinces Lovell to challenge the big toy companies and create an entirely new doll that embodies qualities she respects. The doll is named "Lisa Lionheart." The company that produces Malibu Stacy responds by introducing "Malibu Stacy Plus," the same old doll with a new hat. At the Krustyburger, Grampa realizes that he really belongs on the other side of the counter, with all the grumpy, complaining old men.

On the day of Lisa Lionheart's debut, children flock to the new Stacy doll, ignoring Lisa Lionheart. Lisa concludes that even if her doll makes an impression on just one little girl, her efforts will have been worthwhile.