The Simpsons' 18th season aired from September 10, 2006 to May 20, 2007. The season contained seven hold-over episodes from the season 17 production line. Al Jean served as the Showrunner, a position he has held since the thirteenth season.
The season finale, "You Kent Always Say What You Want", was the series' 400th episode. Additionally, the Simpsons franchise celebrated its 20th anniversary, as it has been on the air since April 1987, beginning with shorts on The Tracey Ullman Show.
Season 18 included guest appearances by Metallica, Tom Wolfe, Gore Vidal, Michael Chabon, Jonathan Franzen, Fran Drescher, The White Stripes, Kiefer Sutherland, Mary Lynn Rajskub, Richard Lewis, Phil McGraw, Elvis Stojko, Natalie Portman, Jon Lovitz, Betty White, Eric Idle, Sir Mix-a-Lot, Stephen Sondheim, Cristiano Ronaldo, Meg Ryan, Andy Dick, Peter Bogdanovich, James Patterson and others.
The Simpson family is introduced to Fat Tony's son, Michael, while carpooling and Lisa quickly befriends the quiet boy after all of the other kids avoid him. As a sign of gratitude, Fat Tony has the Simpsons over for dinner and is shockingly gunned down by a rival family moments after Michael tells his father that he would rather be a chef than take over the family business. After Michael turns down the gang’s offer to be the new kingpin, Homer steps up and leads his family on a mob spree. Michael can’t bear to see what the Simpsons have become and invites the rival family over for a surrender dinner where he poisons the food and returns power to his family.
After an outburst at the funeral for Homer's dead Vegas wife, Marge takes Bart to a shrink who prescribes playing the drums over Ritalin. Bart quickly upstages Lisa at a jazz jam and is recruited into a respected trio. A dejected Lisa turns her back on music and pours her heart into rescuing animals from the local pound. Lisa is able to keep her menagerie a secret until a pet tiger attacks her brother. Bart organizes a benefit concert to have his mangled drumming arm operation but has a last minute change of heart and donates the proceeds to an animal shelter in his sister's name.
Marge discovers her gift for carpentry but has to use Homer as a front in order to overcome people’s predisposed prejudices against women builders. Even though he is completely inept, Homer takes credit for all of Marge’s work which causes her to abandon him just before he lands a job rebuilding a historic Springfield rollercoaster. When Homer’s life is in danger while taking the rebuilt coaster’s maiden voyage, Marge arrives and the couple works out their differences just before the Homer careens off the coaster. Meanwhile, Bart uses Skinner’s peanut allergy to force the Principal to do his bidding.
MARRIED TO THE BLOB - Homer ingests a blob from a mysterious asteroid and suffers from unstoppable hunger. After a feeding frenzy that includes hundreds of Springfield residents, Marge confronts Homer who admits the blob exited him early in his rampage. Rather than be destroyed, Homer is put in charge of eliminating the town's homeless population.
YOU GOTTA KNOW WHEN TO GOLEM - Bart steals a clay Golem for Krusty and enjoys having a personal slave until Lisa orders the monster to talk. The family quickly grows tired of the Golem's neurotic personality and creates a clay female counterpart to keep it in line.
THE DAY THE EARTH LOOKED STUPID - The town creates a self fulfilling prophecy of disasters after believing the radio broadcast of WAR OF THE WORLDS to be real. When Kang and Kodos later arrive, the residents find themselves enslaved rather than being made twice the fools.
After getting Bart out of a commitment he made to join the Army at 18, Homer falls prey to a couple of Army recruiters and ends up in basic training. Treating it like a summer camp, Homer infuriates his sergeant by not cracking under pressure from the hazing and humiliation. Marge and Grandpa end-up trapped in the Army as well due to some questionable tactics by the recruiters when they appeal to get Homer out of basic training. The group is put in a mock military operation as terrorists so the Army can show the power and excellence of the new computer system; however, Homer and the others continue to avoid capture and eventually leave the operation to get food in Springfield where they are mistaken for real terrorists. After leading the military on a humiliating chase through town, Homer is able to take down the US Army by threatening them with the power plant.
While doing a school report on Moe, Lisa discovers his dark poetic talent and helps get him published in “AMERICAN POETRY PERSPECTIVES”. The poems earn him and the Simpson family an invitation to a literary conference in Vermont where rather than be considered a hack by his peers, Moe marginalizes Lisa’s contributions. Moe is later unable to assemble a poem to recite and ends up saving face with Lisa by reciting a sentimental piece about their friendship that bombs his career.
Homer is fired from the plant and quickly lands a successful career as an ice cream man. Marge feels she is constantly being overshadowed by Homer's many careers (astronaut, Krusty impersonator, etc...) and she starts creating popsicle stick sculptures to work through her depression. The pieces quickly takeoff and Marge believes she'll rise out of Homer's shadow at an art opening until Homer (who is being chased by the ice cream Mafia) crashes his truck into the event and sets the pieces on fire. Marge believes the accident was a deliberate attempt at making sure she is never as happy as her husband and she begins ignoring her family. Marge later realizes her error and reconnects with her husband by making a giant statue of a near nude Homer in town square.
Bart becomes Nelson’s best-friend when Marge forces him to attend Nelson’s b-day party that Bart has convinced everyone else to skip. Under the protection of Nelson, no one can mess with Bart, however, Bart can’t hang out with Milhouse anymore. Meanwhile, Lisa and Homer bond over a fantasy book that he reads her each night before bed. Homer gets sucked into the book and reads ahead, when he discovers that the book ends with sad news, he creates a story to tell Lisa to protect her from the truth.
The Simpsons are stuck with an unwanted houseguest after they open their home to Gil for the Christmas holidays. After a year, a failed attempt at getting him a job and many failed "accidents", Marge grows a backbone and throws him out on Christmas Eve and the family is happy once again. Meanwhile, Bart is able to keep off sweets for a year and Lisa keeps her promise of putting on a musical in her brother’s honor.
When Marge’s childhood home movie is played at the Springfield film night, she rediscovers a world that she has forgotten about. Trying to make Marge happy, Homer takes the family on a trip to Barnacle Bay only to discover it is now rundown because their main source of income, the yum-yum fish, have disappeared. After Homer gets the locals to clean up part of the boardwalk, the firework display sets the carousel on fire and his punishment is to go to sea with the fisherman. Out at sea, a massive storm demolishes the boat and the town thinks all is lost until the crew show up at their own memorial service.
Homer's misguided revenge on Cletus combined with an untimely car break down leaves the Simpsons telling tales of revenge gone wrong. Stranded on the side of the road, Marge offers a cautionary tale of revenge from nineteenth century France where French Homer is charged with treason and thrown in jail when Moe sets him up. It takes French Homer three years to plan his revenge and escape only to realize that he wasn't missing much and would rather be back in prison. Lisa tells the tale of nerd revenge at school. Milhouse leads the nerds as they fight back except the power shift causes Milhouse to become power hungry and bullies everyone else at school. When power is taken away from Milhouse, the bullies' revenge is worse than ever. And Bart's story is about the Red Revenge who is searching for the man who killed his parents. He becomes a great crime fighter until he tracks down and destroys the man on whom he was seeking revenge. However, once he catches the man, the Red Revenger quits crime fighting and someone suggests killing another one of his family members to keep the vengeance fighting going.
Lisa invents a family history including a fake Native American tribe to impress everyone for the diversity project at school. As she gains more notoriety for her incredibly detailed story, Lisa feels more and more guilty yet keeps the farce alive hoping it will all blow over. When she finally admits to the fabrication, she must endure sensitivity training. Meanwhile, Bart discovers a nearby town and meets a girl who he thinks got pregnant from kissing him – his first kiss. They decide to run away and get married to start a new life together because the girl is afraid of telling her parents about her situation.
A famous documentarian walks us through the lives of Springfield's prominent inhabitants (Homer, Marge, Moe, Frink, etc...) from childhood to the present. After a failed attempt at convincing the filmmaker that he is a millionaire, Homer is able to regain his pride by hearing how the townsfolk envy his family life.
Told and sung in the vain of “The Sound of Music,” Lisa tutors Cletus’s seven children and introduces them to the outside world. Krusty notices the children’s ability to sing and signs them to be a part of his traveling show. Eventually, the kids get out of their contract with Krusty with the help of Lisa and Cletus’s wife, Brandine. Meanwhile, Bart visits a psychiatrist when he is caught making up a scary story in school.
The court appoints an accountant for Homer when he incorrectly files for bankruptcy, which results in him cutting backing on everything including Grandpa’s nursing home. During his stay at the Simpson house, Selma and Grandpa share a moment during a babysitting stint. Ultimately, Selma and Grandpa get married which leads to disastrous results when they move in together.
Homer's desire to make a quick buck to pay for fire damage on the house turns him into a paparazzi. As the Springfield celebrities become increasingly disturbed by Homer’s aggressive style, they fight back by selling a magazine filled with disturbing pictures of him.
Marge discovers the internet and joins a popular role playing fantasy game. Through exploring the world of “Earthland Realms,” Marge discovers that Bart is the game’s best and most destructive player. All other players are in fear of his presence. During a confrontation in the game, Bart accidentally kills Marge’s character. They eventually reconcile when Bart sacrifices his own character’s life in order to resurrect Marge’s alter-ego. Meanwhile, Lisa has taken up soccer. Homer referees her match when no one else volunteers. Lisa’s competitive streak takes the better of her and she quickly tries to take advantage of the fact that Homer is overseeing her game. Ultimately, Homer kicks Lisa out when she violates some rules. By show’s end, Lisa realizes that she went overboard with soccer and vows to play for fun only.
The Springfield Isotopes is on the verge of winning its first Little League Championship until Bart drops an easy pop fly. Reactions from the townspeople are very harsh and Bart becomes distraught over the level of negative attention. In an effort to cheer up Bart, Lisa introduces him to Bill Buckner. Predictably the meeting does not go well when Bill Buckner starts heckling Bart himself. Unbeknownst to Bart, Lisa and Marge come up with an idea to replay the last inning of the game. Everyone is on board including all the fans and opposing team. After many attempts, Bart finally catches the easy pop fly. Meanwhile, Homer gets a job as a mattress salesman and helps Reverend Lovejoy pick out a new mattress that will improve his love life with his wife.violates some rules. By show’s end, Lisa realizes that she went overboard with soccer and vows to play for fun only.
Homer volunteers as a fire fighter (with Moe, Apu and Skinner) when Springfield’s real fire dept becomes injured. Getting used to people’s gratitude toward them, Homer’s team abuses their authority and starts to steal items from places that are deemed “fire damaged.” Marge and the kids find out what Homer’s doing and make him feel guilty for his acts. In the end, through courageously saving Moe and Apu from a burning building, Homer convinces them to stop stealing as well.
After successfully locating and rescuing Homer from a corn maze, Santa’s Little Helper is recruited to be a police dog. Santa is teamed with a grizzled veteran cop named Lou. The team ends up arresting a known drug dealer; however, he is set free when it is revealed in court that Santa’s Little Helper violated police code. Upset by the injustice, Santa becomes jaded and bites Bart when he tries to surprise him. Santa is subsequently sent to live with Lou. Trying to help Bart cope with his loss, Marge and Homer agree to buy Bart a python. During a show and tell session at school, Bart’s python escapes and accidentally releases a toxic cloud from the science lab. Santa ends up rescuing Bart from the toxic cloud and they are reunited once again.
In the vein of “24,” Bart (in the field) and Lisa (at CTU – Counter Truancy Unit) must stop the bullies (Dolph, Kearney and Jimbo) from releasing the ultimate stink bomb at the school’s annual bake sale and release it at the school bake sale.
Kent Brockman utters a swear word on live television when coffee is spilt on his lab. Patrolling the airwaves for indecent material, Ned starts a campaign to protest Kent and his news station. The FCC fines the station and Kent gets demoted and eventually fired. With Lisa’s help, Kent webcasts the truth about media’s ownership by big corporations (ala “Good Night and Good Luck”). In order to stop his rants, his former station (controlled by the Republican party) offers him his old anchor job back and Kent accepts.