Homer surprises the family with a newly decorated basement, now a recreation room with a pinball machine, a ping-pong table and other luxury items, prompting Marge to ask how Homer could afford all this. He says he has a plan and in the next scene files for bankruptcy before Constance Harm, believing that this will save him from paying his debts. Unfortunately, Harm tells him that the bankruptcy laws have changed and, under the new laws, he has to pay everything back. When looking though the family's expenses, Homer decides to save a lot of money by moving his father out of the retirement home and having him live with the family. The recreation room now doubles as Grampa's bedroom.
Homer and Marge go out one night and ask Grampa to babysit Bart and Lisa. Not entirely trusting Grampa's competence as a babysitter, Marge also asks her sister Selma Bouvier to come over and watch Grampa watch the kids. During the evening, Grampa and Selma end up kissing and eventually fall in love with each other, and are unaware that they are caught by Homer, much to his dismay, as he wants his dad to end up old and lonely. However, just as she was when Abe previously dated Selma's mother Jacqueline in "Lady Bouvier's Lover", Marge is happy with the arrangement, noting that Selma and Abe are like a yummy hot dog made from the parts of a pig no one wants. Patty is no happier than Homer and she enlists his help to break them up. Patty impersonates Selma and Homer dresses up as "Esteban de la Sexface", a Spanish lover-type, and the two arrange for Grampa to catch them kissing. Their plan is foiled though, when the actual Selma comes by and catches them. Angry at being manipulated, Grampa proposes to Selma and she accepts. They get married and move in together.
With Abe unable to find work, Selma is the sole breadwinner in the family, working hard in her new, more stressful job as department manager at the DMV. Abe, meanwhile, destroys their kitchen with his ignorance of how things work by misusing the appliances, causing a kitchen fire. This makes Selma realise that maybe love is not everything you need after all, and she dances with him one last time. They presumably divorce, with Grampa moving back to the retirement home and Selma moving back to her and Patty's room at Spinster Arms Apartments.
Kicked out of the rec room, Bart and Lisa order a lot of complimentary shipping boxes from the A.S.S. (American Shipping Services, not affiliated with the human ass), getting the idea from Ned Flanders, and build a fort out of them. When the Wiseguy becomes angry and asks for them back, they refuse, whereupon he threatens to come back and get them by force (while using a cliche Lord of the Rings accent). Bart and Lisa think he is bluffing, but in fact he comes back with an army of delivery men and women. Bart and Lisa put up a brave fight, first by releasing a barrage of cardboard tubes to trip the enemies, then using cardboard squares to throw like shuriken. The delivery men and women set up a siege ladder and Lisa wraps the lead man in tape and pushes the ladder down. They are aided by Nelson, who arrives unexpectedly to aid Lisa, who could have been hit by a barrage of cardboard arrows. He dives down with twin cardboard tubes and fends off a large number of delivery men and women, while one of the enemies flies overhead, upon a giant, red Fell Beast.
The army swarms while Bart uses a cardboard tube to shoot down enemies with bricks, beehives, egg cartons and Snowball II. The A.S.S. legion fails and flees, but the kids immediately lose interest in their fort and melt it with the garden hose (ignoring the dead Fell beast nearby).