After Homer uses his narcolepsy diagnosis as an excuse to be lazy, he and Marge go through a trial separation, during which Homer dates a pharmacist and Marge dates the pharmacist's father.

Homer is assigned to buy a new washing machine to replace the family's old molding one, but finds a barbecue grill and buys that instead. Later, Bart and Lisa search for the grill when it is stolen right after he was challenged to a cookoff.

Jacqueline decides to reveal the truth: her husband died because of lung cancer, but didn't say so before because back then, people were reluctant to admit it. This revelation shocks Patty and Selma, who decide to quit smoking once and for all and burn all their cigarettes, which unfortunately causes Jacqueline's house to burn down. However, Selma resumes smoking shortly after, causing an angry Patty to move in with Marge and Homer, much to the latter's dismay. Meanwhile, when Maggie makes some new animal friends, she must go on a rescue mission when one of them is taken by Cletus.

After costing salesmen their job, they invade the Simpson household to get revenge on Homer. Meanwhile, Lisa starts becoming scared of everything after she experiences Horror Night at Krustyland, so Homer takes down his Halloween Everscream Terrors decorations to avoid scaring Lisa. In another subplot, Marge takes Bart to a trick-o-treating party because Homer had to take down the decorations, but Bart gets upset when she can't get in due to the party being for residents only.

Guest stars: Blake Anderson as Dickie and Nick Kroll as Lem

In the twenty-sixth annual Simpsons Halloween special, Sideshow Bob finally kills Bart, Homer appears as a sea monster in a parody of Godzilla, and Lisa and Milhouse get superpowers from radiation, with poor Bart somehow missing out and Maggie joining the fun.

Lisa becomes friends with a rich girl named Harper, whose father becomes friends with Homer, but Lisa becomes concerned that Harper is a little too entitled.

When Homer loses his job due to Marge's social media post, he resumes working as a dishwasher at a Greek restaurant he worked when he was in high school. Meanwhile, Lisa works with her new coding teacher to create an app that can predict the effects that any post on social media will have.

Bart experiences early puberty after drinking a milk substitute filled with bad hormones, and ends up competing with Skinner for the affections of his new teacher, Mrs. Berrera. Lisa experiences early puberty as well from the milk, and starts to wear makeup and gets a new hairstyle to look more feminine, netting her popularity from her classmates.

Sanjay's son Jay takes over the Kwik-E-Mart, but Apu is displeased when he turns it into a food market. Meanwhile, in an attempt to get Apu his store back, Homer tries to get Bart to prank the new store, despite the fact that he told him he wouldn't prank anymore.

On Valentine's Day, Professor Frink makes himself attractive to women by using science to transform himself into a more attractive man. Meanwhile, Marge, Bart, and Lisa visit Grampa and try to rescue the old folks from a drug-induced hallucination that allows them to relive their happiest memories.

Bart and Lisa take in a homeless woman to live with them, where they discover that she is a talented folk singer. Meanwhile, Homer accidentally traps the cat in the walls of the house.

Lisa becomes a veterinarian after performing CPR on a raccoon, and learns a harsh lesson when the neglected class hamster, Nibbles, dies. Meanwhile, Marge makes a little extra money cleaning up crime scenes.

Lisa signs up for the Mars One Space Colony, and Marge comes along to try and talk her out of it.

After Smithers is crushed by Mr. Burns' lack of affection towards him, other characters attempt to find a boyfriend for him. Meanwhile, Milhouse competes against a new boy for the lead role in a school production of Casablanca, so he can act alongside his own unrequited love, Lisa.

When Marge tells Homer that she doesn't like Lisa's jazz, Lisa overhears this and gets mad at Marge for lying. Marge wants to restore her relationship with her daughter, so they take a weekend trip to Capital City to attend a performance of Bad News Bears: The Musical, however, Lisa becomes depressed during the trip. Meanwhile, Bart teams up with Maggie to trick people, after he becomes frustrated that everyone knows his pranks.

The Simpson family goes on a trip to Paris, and Homer becomes the courier of a secret briefcase.

Marge gets arrested after Bart goes to the park unsupervised, which leaves Homer struggling to manage the household.