One snowy day in Springfield, Lisa informs Bart that she and Maggie share a bond that Bart will never understand because he doesn't have a brother, so Bart asks Homer for a baby brother. When Homer denies Bart's request, Bart makes his way to the Springfield Orphanage to find what he thinks he's missing.

Grampa is sitting on a bench waiting for his family when a thoughtful-looking man named Marshall Goldman approaches him and asks to hear about his life. Grampa tells Goldman about the time he was on a World War II battleship, which was hit by an enemy torpedo, and Goldman, a human-interest columnist, publishes it in The Springfield Shopper. Later, Grampa meets Mitch Albom and shares another story with Goldman for a follow-up article. Homer becomes jealous of Grampa's newfound fame and seeks a surrogate father. But when Homer discovers a draft of Goldman's third story, he must race to find Grampa before it is published and his life is changed forever.

Homer blows off Marge to buy a lottery ticket and winds up winning the million-dollar jackpot. Fearing how Marge will react if she finds out the reason Homer missed their date, Homer keeps his newly inherited fortune a secret and spoils his family with “anonymous” gifts. When Bart finds out, he and Homer spend the money like it’s going out of style, including buying front-row to tickets to see Coldplay in concert.

When Bart fails to turn in his homework, Mrs. Krabappel sends a letter home about Bart's behaviour. Despite Bart's best efforts to intercept it, Homer reads the letter, and he and Marge visit Principal Skinner for a parent-teacher conference. Furious, Homer punishes him, but Marge takes a more sympathetic approach. When Bart realizes he can pit Homer and Marge against each other to his benefit, his scheming reaches new heights.

Homer takes Marge out for a romantic evening of ice skating and hand-holding, but upon entering the rink, they encounter a curling team practising. Marge and Homer take to the ice and discover their love for the sport, and soon after, join the curling team and compete with them in the Olympic trials. Team Springfield claims the win and moves on to the 2010 Vancouver Games where Bob Costas covers the action. Meanwhile, sleazy vendors introduce Lisa to the world of collecting Olympic pins, and before long, Lisa is hopelessly addicted.

When Miss Hoover asks her students to research their family history, Lisa is horrified to discover that most of her ancestors were bad people – a motley crew of horse thieves and deadbeats. But while rummaging through the attic, Lisa happens upon a diary kept by her ancestor, Eliza Simpson. As Eliza’s story unfolds, Lisa learns that her family was part of the Underground Railroad, a group that helped slaves escape to freedom. Eliza recounts liberating a slave named Virgil, but when Lisa presents her findings at school, some of her classmates refute it, leaving Lisa determined to exonerate her family’s name.

Principal Skinner announces that Mrs. Krabappel was called out of town and budget cuts dictate that, until she returns, the school's two fourth grade classes will merge. Bart reluctantly shares a desk with Nikki and develops a flirtatious rapport. Bart talks to Grampa about his new crush, and at Grampa's suggestion, gives Nikki a kiss. But when Nikki starts sending Bart mixed signals, he swears off women forever. Meanwhile, Lisa's classmates ostracize her for being an overachiever, and First Lady Michelle Obama, a self-professed nerd, comes to Lisa's defence.

When the police are called to diffuse a rowdy crowd at Mr. Burns' estate, one of the officers recognizes priceless stolen paintings on the walls, and the maniacal billionaire is taken downtown for questioning. With Mr. Burns gone, Smithers takes charge of the power plant. But when employees take advantage of his good nature, he exacts revenge by forcing the employees to work night and day. These unfair working conditions prompt Homer and his crew to devise a plan to bust out Mr. Burns.

Homer is completing his court-ordered community service when he befriends his supervisor, Chief Wiggum, by offering him one of his sandwiches. Touched by the act of kindness, Wiggum assigns the other convicts unpleasant tasks, but allows Homer to join him at the picnic table. They continue to grow close, but when the Chief gets injured during a botched bank robbery, Homer doesn't come through when Wiggum needs him the most. Meanwhile, Bart becomes addicted to Battle Ball, a Japanese game made up of plastic balls and magnetic cards, and his family and teachers try to help him kick the habit.

The Simpsons family vacation in Israel with Ned Flanders, but Homer does not appreciate any of the culture—until an Israeli tour guide named Jakob shows him around and, in a severe state of dehydration, Homer believes he is the Messiah.

Bart becomes convinced that his new neighbor, Walt, is his archenemy, Sideshow Bob, disguised and back for revenge. But when Marge tries to convince Bart otherwise by taking him to visit the state penitentiary, a disturbing truth is revealed.

A bomb squad mistakenly blows up Homer's unattended gym bag, releasing radiation into the city and authorities react by suspending civil liberties. Wiggum and his men install surveillance cameras around Springfield and round up suspected terrorists, including groundskeeper Willie, but when monitoring the nonstop flow of video imagery proves to be too much, Wiggum enlists concerned citizens to help keep the city safe. Meanwhile, Lisa becomes fed up with being blonde, so she dyes her hair a dark color.

As Mother's Day approaches, Moe narrates an episode in which he writes a letter to Homer, Apu and Reverend Lovejoy, who are vacationing with their children, and threatens to run away with one of their wives. While the trio tries to determine whose wife Moe is referring to, Homer, Lovejoy and Apu flashback to the intimate moments they initially ignored between Moe and Marge, Manjula and Helen Lovejoy. But when the boys return from their trip, they're in for the surprise of their lives.

The Simpsons decide to embrace a cheaper, alternate source of energy by erecting a wind turbine in their backyard. But when Homer realizes some of the power is being directed to the local electric company, he decides to remove his home from the grid and becomes completely dependent upon an unreliable source of power. Meanwhile, a storm erupts, trapping a magnificent 150-foot-long blue whale ashore, and Lisa and Homer attempt to help the poor creature.

When Moe discovers a hidden talent for judging contests, he is approached by a television agent to join the AMERICAN IDOL judges' panel. Moe flies to Los Angeles where he tours the Fox lot and receives some sage career advice. Meanwhile, Homer drives Marge crazy when he begins hanging around the house.

Worried about the effects of violent video games, Marge encourages Bart and Milhouse to play board games; Lisa becomes smitten with a new student, a vampire; while on a second honeymoon, Homer and Marge rescue a castaway who escaped from his ship.

Grampa gives each family member a portion of his savings; Lisa worries that Nelson's instant success with a new business venture might lure him away from continuing his education.

Lisa starts coaching Bart's Little League team; Marge and Bart spend the day at an amusement park, where former MLB manager Mike Scioscia gives Bart advice.

Homer ends up in the Springfield penitentiary after getting caught bribing an official; an FBI investigator offers Homer a way to reduce his jail time.

Fearing that she will end up like Marge, Lisa pledges to focus solely on her academics and not get distracted by other things; Bart puts Nelson in his place and unintentionally earns the title of school bully.

Marge sends Lisa to a performing arts camp, where counselors and fellow campers inspire her to embrace her creative side; upon returning to Springfield, Lisa grows restless with her boring suburban lifestyle.

When the rest of the family seems to lack Christmas spirit, Marge contacts Martha Clause.