Lisa fears that Homer has become a domestic terrorist when he returns from a nuclear power convention a changed man.
Homer wreaks havoc in Springfield; when Bart is beheaded, his body is attached to Lisa's body; things go awry at Mr. Burns' traveling circus.
After a funeral, Homer, Marge, Mr. Burns and Kent Brockman work to right past regrets.
Marge encourages Homer to cross an item off an old to-do list by inviting an old pen pal to visit; Lisa institutes an honor code at school.
When Homer helps a woman give birth in an elevator, he forms an emotional attachment to the baby; cheerleaders for the local professional football team recruit Lisa.
Lisa is dismayed to learn that her new friend is a Republican, and that they are running against each other for the post of second-grade representative.
Principal Skinner gives the students a blank slate and promises the best-behaved among them can ride in a submarine; Lisa tries to help Krusty with his financial problems.
When a leak at the power plant causes snowfall in Springfield, tourists inundate the town; Marge takes on boarders to raise cash for the holidays.
Home is thrilled to learn how to download pirated movies, and begins screening them in his backyard, but his fun ends abruptly when the FBI arrives on the scene.
When Comic Book Guy meets a woman writing an autobiographical manga, he seeks Homer's advice on dating.
When Marge tries Homer's new high-tech glasses on, he learns she's seeing a marriage counselor; Bart refuses to buy Nelson a Valentine's Day card.
A recent transfer student named Diggs (Daniel Radcliffe) rescues Bart from a confrontation with bullies.
During a research trip, Lisa learns that Sideshow Bob is the chief scientist at a big chemical engineering company; Marge tries to teach a teen church group about healthy sexual practices.
When Retirement Castle is closed, Marge asks Grampa and two other octogenarians to move in; Nelson befriends Bart after Bart defends him.
When Marge and Homer buy a painting at the Van Houtens' yard sale, the couples find themselves at odds when the painting turns out to be worth a lot of money.
When Lisa praises Homer's integrity, he is asked to be a World Cup referee; a slick gangster tests Homer's honesty.
Lisa dates a competitive eater; Bart benefits from helping convict Snake Jailbird escape from a jam.
In the future, a new clone of Homer is created each time he dies, Lisa's husband is a zombie-version of Milhouse and Bart has custody issues with his ex-wife.
When Bart's voodoo doll spell accidentally makes his teacher pregnant, he becomes a savior to couples hoping to conceive.
Homer must figure out what to do when he wakes up to a world where everything and everyone is made out of Lego bricks.
Marge swears off making friends after Homer offends their new neighbors but reconsiders when Lisa decides she doesn't need friends either.