For purposes of this list, "one-time" means they were central to an episode one time. Some of the characters listed here have appeared in later episodes, but only briefly. The characters are sorted by episode.
Cowboy Bob (Albert Brooks), owner of Bob's Roundup RVs. He has non-speaking cameos after this episode, makes a brief speaking appearance in the season sixteen episode "Mobile Homer", and is seen in the episode "Bart Gets an F".
Jacques (Albert Brooks) is a bowling instructor who pursues an affair with Marge Simpson. Jacques has made non-speaking cameos in subsequent episodes, such as "Homer and Apu" (in the Monstro-Mart's line of single, pathetic men who only pay cash for their groceries and do not chat with the clerk) and "Homer's Triple Bypass" (in the waiting room with his bowling ball stuck on one of his fingers). He makes a quick appearance on the bowling team 'The Homewreckers' in "Team Homer", losing to Homer's team the 'Pin Pals'. He is also seen being startled by Bart on his skateboard (along with Bleeding Gums Murphy, Barney, Helen Lovejoy, Moe Syzlak, Chief Wiggum and Apu) in the opening credits of each episode (up until the middle of season 20, when the opening was changed for high-definition TV and the characters on the street were changed). He has a small speaking part in the beginning of Homer vs Lisa and the 8th Commandment, as 'Jacques the Adulterer'.
Gulliver Dark (Sam McMurray), a lounge singer and playboy. After Homer's speech about how women should not be seen or treated as sex objects, Dark decides to call his mother, as she sounded depressed the last time he called her. A man who looks and acts similar to Gulliver Dark is seen singing Tito Puente's fiery revenge song about Mr. Burns on the season seven premiere episode, "Who Shot Mr. Burns?" (Part 2).
Adil Hoxha (Tress MacNeille), a foreign exchange student from Albania who replaces Bart when he is deported to France. Although his good behavior fools Homer and Marge, Lisa is not deceived by Adil's charade and suspects he is up to no good. Her suspicion proves true, as he is actually an Albanian spy who plans to use Homer to gain blueprint information on a reactor for a nuclear power plant. Adil is returned to Albania in exchange for an American spy, also a child, caught in Albania. His last name is an unintentional reference to deceased Albanian leader Enver Hoxha, as stated by Al Jean in the DVD commentary for this episode.
Ms. Botz/Lucille Botzcowski (Penny Marshall) is an escaped criminal, known as "The Babysitter Bandit", who tries to rob the Simpson family, but is thwarted and captured by Bart, Lisa, and Maggie (the kids nearly torture her into insanity by making her watch "The Happy Little Elves"). Before she is revealed on a television show, America's Most Dangerous, Ms. Botz is able to put Bart in his place due to her dealing with previous troublesome children. She deceives Homer into freeing her moments before the police arrive. In "Bart's Dog Gets an F" a news broadcast mentions that she has escaped from prison. In "Hurricane Neddy" she has a non-speaking cameo as a patient at Calmwood Mental Hospital; and also appears in a cameo in Family Guy episode The Simpsons Guy. In The Simpsons: Bart vs. The Space Mutants she appears as a Springfield Mall Boss who tries to drop luggage onto Bart Simpson-who manages to deflect it back on his old nemesis.
Karl (Harvey Fierstein) is Homer's assistant who tries to help Homer succeed as an executive. When Homer is about to be fired for his misdeeds, Karl takes the blame and is fired in his place. Karl is the first openly gay character on The Simpsons and kisses Homer after getting fired.
Beatrice "Bea" Simmons (Audrey Meadows) was Grampa Simpson's girlfriend. They met at the Springfield Retirement Castle. After arranging a date for Bea's birthday, Grampa was forced to stand her up when Homer took him to "Discount Lion Safari". When he returned to the Retirement Castle, Bea had died and left all her money to Abe. It was Bea's death that made Abe resent Homer for his actions and eventually used the money to renovate the retirement home, dedicating the dining hall in her name.
Professor Lombardo, (Jon Lovitz) an art teacher at Springfield Community College. He is quick to compliment almost everything he sees as art. However he does not take praise very well. He reappears briefly in "The Ziff Who Came to Dinner" as part of a quartet of Simpsons characters who were voiced by former SNL cast member Jon Lovitz.
Mr. Bergstrom (Dustin Hoffman, credited as "Sam Etic") was Lisa's substitute teacher. Mr. Bergstrom took over for Ms. Hoover after she believed she had got Lyme disease and Lisa immediately took to him because he was the kind of male role model she needed in her life. However, after Ms. Hoover returned, he had to leave Springfield. A distraught Lisa ran to stop him, and Mr. Bergstrom gave her a note saying "You are Lisa Simpson". He later makes a brief non-speaking appearance in the 25th-season episode "The Kid Is All Right" and in season 27 in the episode "Friend with Benefit".
Leon Kompowsky (voiced by Michael Jackson, Kipp Lennon and Hank Azaria) was a mental patient who pretended to be Michael Jackson. The character was voiced by Michael Jackson (who, for contractual reasons, was credited as "John Jay Smith"). The producers of the show were legally prevented from confirming Jackson guest starred at the time, although many media sources (correctly) assumed it was really him. A year after the episode aired, the writers decided to make a sequel where Leon Kompowsky returns, thinking he is the musician Prince (and voiced by Prince himself), who encourages everyone in town to be sexually liberated, but it was scrapped when Prince declined.
Bob Arnold (Hank Azaria) was a corrupt Congressman. He accepted a bribe to demolish Springfield National Forest, but was overheard by Lisa Simpson, and was later caught and arrested after she exposed him while making her speech along with a sexist comment he made about a feminist statue.
Crippled Merchant (Hank Azaria) is a Moroccanstreet vendor who sells Homer a monkey's paw. He was once the President of Algeria because of a wish he made on the paw. He warns the Simpsons not to use the paw to make their wishes unless they want to suffer great misfortune. Out of the Simpsons, only Marge heeded the merchant's warning.
Collette (Jo Ann Harris), a waitress hired by Moe because of her moxie. Catherine O'Hara originally agreed to do the voice and recorded her part for the character; however, the producers felt that her voice did not fit the role and instead had Jo Ann Harris do the part.
Mr. Black (Harry Shearer) was Krusty's accountant and the evil camp director of Kamp Krusty who hires local thugs Dolph, Jimbo, and Kearney to be counselors to break the kids' spirits (which does not work when Bart leads an insurrection against them). He promptly flees on a hydrofoil, never to be seen again. Mark Kirkland was sure that the character was going to reappear later in the series, but he never did. However, he appears in a comic book based on the series where he has Homer sell him a company while "filling in" for Moe, who was literally tied up down in his basement.
Llewellyn Sinclair (Jon Lovitz) is an intense, short-tempered perfectionist who works as a theater director. He boasts of the multiple heart attacks he has suffered for his work. He casts Ned Flanders as Stanley Kowalski and Marge as Blanche DuBois in a production of A Streetcar Named Desire. Sinclair has since made brief cameo appearances and appeared in a crowd shot in "Sweets and Sour Marge". He also appeared with speaking parts in "I'm Just a Girl Who Can't Say D'oh".
Amber Dempsey, (Lona Williams) a professional child beauty queen who once won Pork Princess and Little Miss Kosher in the same week. She has eyelash implants (which are only legal in Paraguay) and is referred to by Lisa as "the Jack Nicklaus" of the pageant circuit (not because they're attractive, but because they both win all the time). Amber wins The Little Miss Springfield Beauty Pageant, but the crown is turned over to Lisa (the first runner-up) after Amber gets struck by lightning during a store opening. She is hospitalized and quickly becomes "Little Miss Intensive Care".
Jack Larson (Harry Shearer), is president of Laramie Cigarettes, and once owned the Springfield Isotopes. He also was the spokesperson in a commercial for the Little Miss Springfield pageant, with Laramie cigarettes as the main sponsor.
Laura Powers (Sara Gilbert) is the teenage daughter of Ruth Powers. Her first and only speaking appearance is when her family moved next door to Bart after the elderly Winfields moved out. Bart developed a crush on her, but ended up in heartbreak when he found out her boyfriend was Jimbo Jones, whom she later breaks up with after Moe threatens to kill him over a prank call that Bart made and Jimbo breaks down sobbing. Ruth mentions Laura in "Marge On The Lam" 
Lyle Lanley (Phil Hartman) is a smooth talking con man who uses songs to convince the people of Springfield into buying an expensive monorail after Mr. Burns was fined $3 million. However, Lyle finds an enemy in Marge, the only resident who opposes it. Suspecting he had an ulterior motive, she discovers his plans in using the money he skimmed from the shoddily-built monorail to go on vacation without concern for the Springfieldianites. However, an angry mob of North Haverbrook residents attack him during an unexpected flight layover, their city having previously fallen for his monorail scam. The character is based on Harold Hill, the main character from the 1962 film The Music Man.
Sebastian Cobb (Harry Shearer) A German scientist living in North Haverbrook who built the monorail for Lyle Lanley. Like Marge, he opposed the building of the monorail.
Tom (Phil Hartman) is Bart's "Bigger Brother". Bart decides to get a bigger brother after Homer failed to pick him up from soccer practice. At the aquarium, Homer got into a fight with him. At the end of the episode, he became Pepi's big brother. The part was written for Tom Cruise, but Cruise declined so the role was given to Phil Hartman instead.
Pepi (Tress MacNeillie) is a poor boy who lives in Springfield and becomes Homer's 'Little Brother'. At the end of the episode, he becomes Tom's 'Little Brother' after Homer and Bart reconcile.
Sideshow Raheem (Michael Carrington): the militant black Sideshow partner Krusty had on his show in the 1970s. Has an Afro and wears a dashiki and dark sunglasses. Was seen at Krusty's funeral on "Bart the Fink".
Rex (Michael Carrington): a melodramatic boy in Lisa's class who auditioned to play George Washington during the school's Presidents' Day pageant. Although impressive, he was turned down for Ralph Wiggum by Ms. Hoover (so she can have the Denver boot removed from her car tire) and tried to claim it was fair. Rex suspected that Ralph only won the lead role because of his father's position as the Springfield Police chief and resented being cast as George Washington's butler who appeared near the end of the performance. Another boy with a similar personality to the Rex in this episode appeared in season six's "Bart of Darkness," but his appearance was drastically altered, looking somewhat like Hugh Parkfield, the Englishman Lisa almost marries in "Lisa's Wedding."
Dr. Wolfe (Hank Azaria) is the intimidating and judgmental dentist that the Simpson family visits. Anthony Perkins had agreed to voice Dr. Wolfe, but unfortunately fell ill and could not record the part. Clint Eastwood and Anthony Hopkins had also been asked to provide a voice, but both declined. Perkins was then asked and while he expressed interest, he died before recording. The role went to Azaria.
Nigel (Harry Shearer) An Englishman and manager of the Be-Sharps. He suggested the band should replace Chief Wiggum with Barney Gumble because the former was "too Village People", and convinced Apu to adopt the stage name Apu de Beau Marchais. He pushed the group to choose a name and go public.
Dean Bobby Peterson (Hank Azaria) Dean of Springfield Community College. Homer psychologically projects onto him the role of an uptight, intolerant dean that he's seen in film, despite Peterson's friendly and laid-back demeanor, even forgiving Homer for hitting him with his car. The character made a brief speaking appearance in the episode "Faith Off" looking and acting completely different.
Brad Goodman (Albert Brooks) is a self-help guru. After talking to Bart Simpson during a lecture at Springfield, he encourages the town to be more like Bart and to "do what you feel like", which eventually causes disastrous consequences. The people of Springfield go so far as to construct a golden statue of him in a parody of the biblical golden calf. His is the third character to be voiced by Brooks in the show.
Molloy the Cat Burglar (Sam Neill) is a thief and cat burglar who steals many objects from the townspeople of Springfield, including Lisa's saxophone. He is later caught by Homer after Grampa reveals the identity of the burglar but escapes while the town searches for his 'buried treasure'.
Stacy Lovell (Kathleen Turner) is the inventor of Malibu Stacy. Was fired in 1974 for funneling profits to the Viet Cong and because "her way of thinking wasn't cost-effective". She lives in an exact replica of her Malibu Stacy Dreamhouse in a neighborhood for recluses and once dated an African-American man who looks like a G.I. Joe action figure.
Freddy Quimby (Dan Castellaneta) is the nephew of Mayor Quimby who is accused of assaulting an extremely clumsy French waiter. He was apparently based off John F. Kennedy Jr. ("John-John"). He reappears in "Trash of the Titans" as one of the people in line at the courthouse to register as a sex offender (along with Patty and Selma, Jimmy the Scumbag from "Lisa's Date with Density," and Moe, who complains about how long the sex offender line always is) and later in "See Homer Run" (with a somewhat altered voice and appearance) as his uncle's press secretary.
Clumsy Waiter (Hank Azaria), is the French waiter who Freddy mocks due to his accented version in pronouncing Chowder. He sues Freddy out of revenge and under the guise that he was assaulted. At risk of being exposed for skipping school by Skinner, Bart gives out his testimony that Freddy is innocent and the waiter is clumsy. The waiter tries to deny this, but trips and falls outside on a truck housing mouse traps, proving Bart's theory true.
Bort, a churlish patron of Itchy & Scratchy Land's gift shop, who coincidentally shares his name with the son of a woman he encounters (as well as innumerable other park enthusiasts, given the wild popularity of the novelty license plates bearing the name on the park's souvenir racks to the point of them having been sold out).
Jessica Lovejoy (Meryl Streep) is the daughter of Timothy and Helen Lovejoy. Initially appearing as a calm, sweet girl back from boarding school, she also enjoys causing mischief, but reveals that she is even more of a wild misfit than Bart; she was actually expelled for destroying school property, stealing and starting up fights. Wooing Bart the first day they met, she soon became his girlfriend, but later revealed a manipulative femme fatale side. Though she only had one major role on the show, she appeared many other times in Simpsons Comics such as when she became fat (along with the rest of Springfield Elementary because Nelson stopped bullying).
Ashley Grant (Pamela Hayden) is a feminist graduate student who babysits Bart, Lisa, and Maggie. She falsely accuses Homer of sexual harassment (albeit unwittingly) after she mistakes his reaching for the candy Venus de Milo stuck to her rear end (complete with drooling) for a sexual attack, prompting a protest and media circus against Homer. Ashley forgives Homer (and vice versa) after she is shown video evidence of his innocence.
Dr. Zweig (Anne Bancroft) is a psychologist who tries to help Marge get over her fear of flying. She appears as one of the judges at Marge's insanity hearing in "It's a Mad, Mad, Mad, Mad Marge". While a competent psychologist, she is somewhat hypocritical as she, as Homer predicted and feared, immediately suspects Homer of responsibility for Marge's problems, despite her statement that she was not there to cast blame on anyone. However, in "It's a Mad, Mad, Mad, Mad Marge", she and her colleagues are somehow completely ignorant of the ubiquitous concepts of religious belief and prayer, instead interpreting Marge's prayer to God and belief in his omnipresence as symptoms of schizophrenia.
Guy Incognito (Dan Castellaneta) is a seemingly upper-class man who is identical in appearance to Homer Simpson. After Homer is banned from Moe's Tavern, Guy Incognito appears at the bar and introduces himself. He is mistaken for a badly disguised Homer and is subsequently beaten up and thrown out of the bar only to have the real Homer walk past him.
Don Vittorio DiMaggio (Hank Azaria) is Fat Tony's boss and a self-admitted Italian American stereotype. He has since made brief non-speaking cameos in later episodes, particularly in the mob meeting sequence on "Insane Clown Poppy".
Evan Conover (Phil Hartman) is a U.S. diplomat who sells out the Simpsons to angry Australian officials.
Tobias Drundridge (Pamela Hayden) is an Australian boy who accepted a six-hour collect call from Bart. His father Bruno (Hank Azaria) alerts the Prime Minister, and Bart is eventually indicted for fraud by the Australian government.
The Fortuneteller (Maggie Roswell), a woman dressed as a gypsy at the local Renaissance Fair who shows Lisa's future in the year 2010 as a graduate student who nearly marries a British man, until she realizes that he hopes to cut Lisa off from her family.
Hugh Parkfield (Mandy Patinkin), a handsome and intelligent British college student whom Lisa nearly marries. He is a parody of English actor Hugh Grant.
Mrs. Burns, Mr. Burns’ 122-year-old mother (though there was another woman who was said to be Mr. Burns' mother on season five's "Rosebud," though she could be the same woman, changed only by age and bitterness for her offspring). She is seen briefly when Smithers phones to tell her she has a call waiting from her son, who she refers to as "that improvident lackwit", but Homer accidentally cuts her off before they can speak. According to Smithers, Burns hates talking to her having never forgiven her for an affair with President William Howard Taft.
Chester J. Lampwick (Kirk Douglas), a homeless man who was the creator of the in-series cartoon character Itchy, which was stolen by Roger Meyers Sr. Lampwick's original characterization and art for Itchy parody Mickey Mouse's first appearance as Steamboat Willie.
Lester (Nancy Cartwright), a young boy who resembled Bart from the Tracy Ullman shorts. He and Eliza helped bring Itchy and Scratchy back to television before Bart and Lisa did after proving an unknown plagiarism. He is last seen skateboarding and briefly spies on Bart with disdain, implied to be blaming the latter for helping Lampwick ruin Itchy and Scratchy.
Hank Scorpio (Albert Brooks) is an evil genius and supervillain. He is also the cheerful, friendly owner of Globex Corporation. Scorpio is considered by some to be Albert Brooks' best voice performance on The Simpsons and for this and four other guest performances he was named the greatest guest star in the show's history by IGN. Brooks ad-libbed many of his lines. He was supposed to be the main villain of The Simpsons Movie, but the character was replaced with EPA chief Russ Cargill (also voiced by Brooks) by the writers.
Scorpio also appears in Simpsons Comics #117 ("Sandwiches Are Forever"), #132 ("A Brand New Burns (Part Two)"), #66 ("Homer's Luv Boat" + "A Top Secret Tour of Globex with Scorpio") and makes a cameo in Simpsons Comic #69 ("How Marge Got Her Curtains Back").
Hugo Simpson (Nancy Cartwright), is Bart's supposedly evil conjoined twin brother who was kept confined in the Simpsons' attic, until it is discovered that Bart was actually the evil twin all along. At the end of the segment, Hugo has rejoined his family and Bart has replaced him in the attic. Hugo Simpson is one of the character costumes for Bart in the video game The Simpsons: Hit & Run.
Larry Burns (Rodney Dangerfield) is the long-lost son of Montgomery Burns. He is lazy and low-brow, and so he and Homer become good friends. While he fails to earn Mr Burns' love, he is consoled when he remembers that he has a wife and children, who are likely wondering why he vanished for a week. He later appears in the unemployment office in "Realty Bites".
Belle (Tress MacNeille) the owner of the Maison Derrière, a local burlesque house where Martha Quimby met her husband, Mayor Quimby. According to the season eight DVD commentary, there were auditions held for a celebrity to voice Belle, but this was dropped in favor of veteran voice actress Tress MacNeille.
Starla (Tress MacNeille), Kirk Van Houten's rebound "special lady" immediately following his separation from Luann. Allegedly a temp at KZOG Radio 530, she told Kirk she would help launch his singing career. Instead, she stole his car and ruined his demo tape, entitled, "Can I Borrow A Feeling?"
Dr. Foster (Hank Azaria), Ned's psychologist as a child who treated Ned in the Calmwood Mental Hospital after his breakdown. He appears again at Marge's competency hearing in "It's a Mad, Mad, Mad, Mad Marge" in a younger form.
Frank Ormand (Jack Lemmon) is the founder of the Pretzel Wagon company who convinces Marge to start her own pretzel-selling business. He later dies in a car accident while Marge struggles to compete with "Fleet-a-Pita".
Shary Bobbins (Maggie Roswell) is a magical British nanny modeled after Mary Poppins and hired to care for the Simpson children after Marge is revealed to be going bald from stress. After realizing she can never make The Simpsons functional, Bobbins flies away, and (unknown to the rest of the family) dies when she gets sucked into the jet engine of an airplane. She reappears in a cameo in "Treehouse of Horror XXV", and possibly among a bunch of flying nannies glimpsed in "The Regina Monologues", and on the opening sequence of the 2nd and 6th episodes of the 21st season, "Bart Gets a 'Z'" and "Pranks and Greens".
Roy (Hank Azaria), a young adult who briefly lives with the Simpson family. Before his introduction Lisa states "Adding a new character is often a desperate attempt to boost low ratings." At the end of the episode he leaves the Simpson house to live in an apartment with two sexy ladies. Before production began, a Fox executive suggested the staff add a new character to the show, who should come and live with the Simpsons on a permanent basis because it would "liven up the show". The staff rejected the idea. Instead they inserted the one-time character Roy, with no explanation as to who he was or why he was there. Roy's appearance, mannerisms, and role all resemble that of episode-centric Itchy and Scratchy character Poochie. This was as a reference to the executive's proposal (and a meta-joke about long-running shows bringing in annoying characters to boost ratings). Roy was originally conceived for the "Time and Punishment" segment of the season six episode "Treehouse of Horror V", living with the Simpsons in an alternate reality where Homer has an annoying teenage son.
While Springfield Elementary students are watching a potential cartoon series, a muscular man in a Speedo capriciously walks onto the screen and starts flexing. Nelson Muntz made it seem like Milhouse van Houten enjoyed seeing him. This upset Milhouse. Roger Meyers Jr. says, "One kid seems to love the Speedo Man." The character may have been based upon the He-Man cartoon character.
John (John Waters), who is voiced by and modeled after John Waters, is the owner of Cockamamie's Collectibles Shop, an offbeat store filled with various "camp" items. Homer becomes friends with him, but breaks it off when Marge tells Homer that John is gay.
Laddie (Frank Welker) a finely-bred, pre-trained collie which Bart buys using his credit card. When Bart realizes he misses Santa's Little Helper (after Bart lets Santa's Little Helper get repossessed when Bart has everything he bought with the credit card taken from him), he gives Laddie to the Springfield Police Force.
Mr. Mitchell (Dan Castellaneta) is a blind man that adopted Santa's Little Helper after Bart sends him away in exchange for Laddie. Bart then goes to retrieve Santa's Little Helper from Mr. Mitchell.
Big Daddy (Gailard Sartain) is a New Orleans-based criminal who steals the Louisiana governor's mansion and kidnaps Ralph Wiggum. He is set up as the primary antagonist of the Chief Wiggum spinoff, whom Wiggum expects to face "each and every week".
Betty (Unknown) is a woman that Moe goes on a date with while using the love tester that has Grampa's spirit.
"Lisa Simpson" (Pamela Hayden) a cheerleader that took over Lisa's place in "The Simpsons Family Smile-Time Variety Hour" when she refused to participate.
The Commandant (Willem Dafoe) is the head of Rommelwood Academy, who is wary of Lisa attending military school, but has no qualms over Bart joining (since Rommelwood Academy is an all-boys school).
The real Seymour Skinner (Martin Sheen), the real Skinner and Armin Tamzarian were buddies in the Vietnam War. After the real Skinner was supposedly killed, Tamzarian stole his name and took over Skinner's life. The resulting episode was one of the most controversial among the fans and is disliked by several members of the production staff, including Matt Groening and Harry Shearer.
Fox Censor (Harry Shearer), a Fox network censor with the same name as his title. He edits a Treehouse of Horror script to lower the rating to TV-G, but then gets stabbed repeatedly by a sword that came from the sign, which goes from TV-PG to TV-14 to TV-MA to TV-21 and TV-666 (the last two of which do not exist on the American TV rating system).
The Leader (Hank Azaria) is the founder of the Movementarian cult. He had people join by telling them they would go to a planet Blisstonia and would take their money to build a rocket ship to escape Earth.
Ray Patterson (Steve Martin) is the former Springfield sanitation commissioner who gets defeated by Homer by convincing the public with "crazy promises". When Homer abuses his power, Patterson is called back, but does not return to his post.
C. W. McAllister is a former friend of Abraham Simpson, who climbed Mt. Murderhorn. Simpson claimed that McAllister betrayed him, but McAllister wrote in his journal that it was Simpson who betrayed him and tried to eat his arm.
Seth (George Carlin) and Munchie (Martin Mull) are two aging hippies/natural juice businessmen, who were friends of Homer's hippie mother, Mona (voiced by Glenn Close). They keep a cache of psychedelic drugs for their personal use which Homer, feeling guilty over a snafu that ruined Seth and Munchie's real harvest, mistakenly uses to make a batch of Seth and Munchie's trademark juice, causing the townspeople drug-induced fantasies. Seth and Munchie also appear in the rally in "Weekend at Burnsie's" and make an appearances in "Mona Leaves-a" at Mona Simpson's funeral.
Pinchy, a pet lobster raised by Homer after being bought live from a grocery store. Homer later became attached to the lobster to the degree of considering him part of the family and not wanting to cook him, until he accidentally gave him a hot bath in the bathtub. Homer is seen eating Pinchy while crying at the end of the episode.
Southern Colonel, a colonel who accepts a duel by Homer after Homer hits him with a glove.
Emil (does not speak), Mindy (Tress MacNeille), and J.P. (Harry Shearer): Executives of Laramie Cigarettes, who hope to purchase Homer's new invention, tomacco, for $150 million (US). He spurns the offer, demanding $150 billion, which they will not pay. They steal Homer's last tomacco plant, but are killed when their helicopter crashes, due to the presence of a tomacco-addicted (and thus insane) sheep on board.
PBS Man (Hank Azaria): An official in the pledge-collecting department of PBS. When Homer mistakenly pledges $10,000 to PBS, this man appears at Homer's house to collect the pledge; Homer then escapes to the bank, where a clerk refuses to give him the money. Homer tries to stab the PBS Man in the heart with a chequewriting pen — which is attached to the counter. He appears again in the ending, hoping to collect money for the FOX Network, to which Bart calls with the purpose of donating $10,000.
Titania (Pamela Hayden), a blond, large-chested female bartender from Juggernauts in Hollywood, California who competes in the Duff Days bartending contest.
Dr. Velimorovic (Hank Azaria), a plastic surgeon who operates on Moe. The doctor also appeared in his second speaking appearance in "Large Marge" (when Marge got breast implants) and "Husbands and Knives" (when Homer becomes obsessed with getting plastic surgery in order to keep Marge).
Mr. Thai (Hank Azaria), is the proprietor of a restaurant named "You Thai Now". He hires Bart to distribute menus. He is later seen at the bidding auction for the logging rights to the oldest redwood tree.
Gabriel (Delroy Lindo), a social worker hired to rehabilitate the Simpsons after they get arrested for fighting with each other while playing Monopoly. He leaves them when he finds out about Homer and Flanders' Vegas wives and isn't seen again.
Garth Motherloving (Ben Stiller), head of the Motherloving Sweets and Sugar Company. He is also the leader of a smuggling gang which attempts to smuggle sugar from San Glucos island into Springfield after sugar and sugar-containing products are banned in Springfield.
Officer Krackney (Charles Napier), a guard at the Montgomery Burns State Prison (formerly the Springfield Culture Center), he is remarkably sadistic and abusive, to the point of psychopathy, and even confessing that he killed his own father when he was a child.
Jenda (Amy Poehler), Bart's high school girlfriend in 2013 who wants Bart to make something of his life, but when Bart takes Lisa's chance at a scholarship, Bart refuses to let his sister down and gets dumped by Jenda. In "Holidays of Future Passed," it's revealed that Bart and Jenda reconciled at an unknown point and eventually married and had two sons together. However their marriage eventually failed. The two have two children who look like Bart and Jenda has kept custody of them after she and Bart divorced and she married her new boyfriend in secrecy.
Ray Magini (Ray Romano), a roofer whom Homer befriends, but is thought to be invisible by everyone around Homer. His name is an anagram of the word "imaginary," which is why everyone around Homer thinks Ray isn't real.
Coach Clay (Harry Shearer), a brash coach who moves in next to the Simpsons after Ned Flanders moves to Humbleton, Pennsylvania. Ends up harassing and taking advantage of Homer, just like Homer harassed and took advantage of Flanders.
Vicki (Pamela Hayden) and Sasha (Tress MacNeille), college students who record themselves in soft-core sexual situations while staying with Ned Flanders.
Gravedigger Billy (Dan Castellaneta) is Groundskeeper Willie's cousin who is a gravedigger at the cemetery next to 742 Evergreen Terrace. He has been a gravedigger for thirty years and walks with a limp. He has a beard and hair identical to Willie's except that he has white hair and a glass eye in his left eye socket. He wears a light-blue waterproof trench coat and rain hat, blue trousers and black boots. In the episode, he steals a watch from a grave and later attacks Willie.
Dr. Egoyan/Manfred Manslaughter (Hank Azaria), an Armenian-American doctor specializing in euthanasia who gives Grampa the option of committing assisted suicide after Grampa costs the town a chance at a football franchise.
Melanie Upfoot (Frances McDormand), Principal Skinner's replacement following the controversy behind his sexist remarks about women's math skills. Orders Springfield Elementary to be segregated by gender.
Tabitha Vixx (Mandy Moore), a pop singer married to Buck Mitchell of the Springfield Isotopes baseball team. She includes a lot of striptease acts in her singing, which makes her husband jealous and uncomfortable.
Buck Mitchell (Hank Azaria), Tabitha's husband and Springfield Isotope professional baseball player.
Michael D'Amico (Tress MacNeille) is Fat Tony's son who becomes Lisa's friend. Michael has a gift for cooking, which he uses to poison his father's rivals and (presumably) breaks off his friendship to Lisa when he does not admit to poisoning his father's rivals. He was mentioned (by name only) earlier in "Moe Baby Blues" and "The Seven-Beer Snitch".
Billy (Maurice LaMarche), "Portuguese" Fausto (Hank Azaria) and the Skipper (Hank Azaria) are three members of the crew of the boat The Rotting Pelican. There are also five nameless ones, one of whom is voiced by comedian/Simpsons writer Dana Gould.
Dr. Stacey Swanson (Meg Ryan) is a psychiatrist who is assigned to treat Bart Simpson. They form a close bond, and after the last session, Swanson is forced to see another psychiatrist.
Dark Stanley is a vengeful cook who suffers emotional bullying from students that taunt him for his ruined life, until he has a psychotic nervous breakdown and starts to serve the same students in his soup. Bart invents this history to scare the other students in order to get their lunches, and later reveals that he gets the name from a hammer that Homer uses to spank him. However, it's later revealed that, somehow, Dark Stanley was real.
Joe LaBoot (Hank Azaria) is a professional baseball player and loser of a World Series game, who dropped a fly ball and continues to be rich and famous. After Lisa takes Bart to see him, LaBoot makes everybody in the building "boo" Bart, causing him to cry.
Louie (Matt Dillon), a tow truck driver who gave Homer a job, but when Homer (unintentionally) violated Louie's territory, became his enemy and held him hostage (with 5 other men in similar circumstances) in his basement. Homer and the others are rescued by Maggie.
Dwight (Steve Buscemi), a criminal who got arrested after a bank robbery. Marge promised she would visit him in prison. However Marge did not and he kidnapped Marge and took her to an amusement park his mom abandoned him at when he was a kid. There he got injured and sent to jail. Marge then visited him in the end.
Milo (Jack Black), a local comic book store owner who works right across from the Comic Book Guy's store "The Android's Dungeon". Unlike the Comic Book Guy, Milo has a girlfriend, is not obsessed with keeping comics in mint condition, and treats his customers with respect.
Dr. Robert Terwilliger Sr. (John Mahoney) is Bob and Cecil Terwilliger's father. He tried to find proof that his son has gone insane due to abuses from Bart. The casting of Mahoney here mirrors his casting as the father of the Crane brothers on Frasier. Actors Kelsey Grammer and David Hyde Pierce portrayed the Crane brothers there, and portray Bob and Cecil Terwilliger in The Simpsons.
Dame Judith Underdunk (Tress MacNeille) is Bob and Cecil's mother and an eminent Shakespearean actress.
Betsy Bidwell (Tress MacNeille), a former obese woman who used to weigh 400 pounds, but becomes Homer's nutritionist and assists with his diet.
Zack (Hank Azaria) the host of a Cheaters-type hidden camera show who only cares about breaking up couples who cheat (be it on another person or, in Homer's case, on their diet) just to get ratings for his show.
Bashir Bin Laden (Tress MacNeille), Bart's new friend from Jordan. He almost gets beaten up by the three bullies (Dolph, Jimbo, and Kearney) for being Muslim, and Homer insults his parents and accuse them of being terrorists because of their religion (Islam).
Juliet Hobbs (Emily Blunt), a strange new girl whom Lisa befriends. Together, the two create a fantasy world called Equalia where the two reign as queens. She runs away from home at the end of the episode and it is unknown if she returns home.
Tom O'Flanagan (Colm Meaney), the owner of O'Flanagan's pub in Dunkilderry, Ireland. Kenneth Branagh had originally been asked guest star as the pub owner and came in to record the part. However, Branagh was replaced by Meaney and did not appear in the episode.
Maya (Tress MacNeille), is a beautiful woman Moe meets over the internet. When Moe meets her in person, she is three feet tall. Despite this they end up hitting it off, even after Moe worried what his friends/patrons would think of her, to which Homer did not even pay attention to her height. Moe came close to making her Mrs. Maya Szyslak, but got too comfortable joking around with her about her height, much to her chagrin. To make it up to her, he tried to literally knock himself down to her size, but she convinced him not to by leaving him for trying something so insane and insensitive.
Jenny (Anne Hathaway) is the beautiful girl who Bart fell in love with. At first she thought Bart was a nice guy, but then she dumped him. She helps out around the Springfield Retirement Castle. She's a Christian and prays to God at school. Bart tricked her into believing that he was something he was not which is the reason he got dumped and left by Jenny. Bart has not seen her since.
Inga (Tress Macneille), Groundskeeper Willie's Swedish girlfriend. She is a bikini model who lives in his shack.
Zachary Vaughn (Hank Azaria): Mrs. Krabappel's replacement teacher after Krabappel is fired (expelled) for drinking alcohol on the job. He is obsessed with social networks and makes the kids use their phones to text instead of actual education.
Andy Hamilton (Jonah Hill): An immature, college-aged man who was once hailed Springfield Elementary's prankster after filling the school's pool with worms and turning Principal Skinner into the strait-laced, no-nonsense disciplinarian he is today. Now writes for "The Krusty the Clown" show after Bart urges Andy to do something with his life.
Princess Penelope (Anne Hathaway): A princess character hired to be Krusty the Klown's wife and sidekick in an attempt to get girls to watch The Krusty the Clown Show. Real name: Penelope MountbattenHabsburgHohenzollernMulanPocahontas. Was a fan of the Krusty show since she was a child; confessed her love for him as an adult. Her father was a station manager for the New York affiliate that aired The Krusty Show back when Penelope was a kid. Sings and plays guitar.
Gator McCall (Hank Azaria): A headhunter (corporate recruiter) who persuades Homer, Lenny, and Carl to work for the Capitol City Nuclear Plant after Mr. Burns cuts free donuts from the budget at work.
Nikki (Sarah Silverman): A girl Bart is forced to sit with when the two Fourth Grade classes are combined, her attitude towards Bart is very fickle, in the end she claims it is because "There are a lot of things Bart doesn't know about girls and Nikki isn't going to tell him".
Mall Cop (Kevin Michael Richardson): A security guard at the Springfield Mall that rides in segways. He caught Shauna Chalmers smuggling a bottle of perfume. Bart then takes the blame for it and escapes from the security guard when he flattens one of the segway's tires, and the guard forgot how to use his legs.
Bongo (later renamed Hendrix): A dog that Abe Simpson owned back then when Homer was a child. He had to give him away to a former neighbour named "Miss Viola" after Mr. Burns wanted him dead. It's unknown if Hendrix is still alive.
Slava (Bill Hader): The father of Zhenya that Marge taught to drive in exchange for Zhenya giving Bart piano lessons.
Zhenya (Jane Krakowski): The daughter of Slava and a piano teacher. Bart took lessons with her and developed a crush on her, while she didn't love him back because of his poor piano skills. She then gets more students when Bart pretends to be a professional piano player with the help of a CD.
Hettie (Kate McKinnon, Natalie Maines for singing voice): A homeless woman whom Bart and Lisa secretly let live in their closet. Bart and Lisa also discover that Hettie is a talented musician. Lisa planned on putting her on a show, but that's when Hettie revealed she was a heroin addict, and didn't make it to the show.
The Simpsons Movie
Russ Cargill (A. Brooks) – Cargill is a businessman and head of the Environmental Protection Agency (abbreviated as EPA). After Homer pollutes Lake Springfield and causes the wildlife to mutate, Cargill presents this information to the President, convincing him to approve a plan to deal with the situation. Cargill lowers a giant dome on top of Springfield, sealing the city off from the rest of the world to prevent the toxic fumes from spreading. Upon hearing of the Simpsons' escape and the citizens' attempts to break the dome, Cargill attempts to have Springfield demolished with a time bomb. Ultimately he tries to kill Homer and Bart with a sawed-off shotgun, but is interrupted by Maggie, who drops a large boulder on his head. The deleted scenes on the DVD shows that Cargill was originally going to be an older man in a sweater vest and quiff.
President Arnold Schwarzenegger (Harry Shearer) – Schwarzenegger appears to be inept, as he is easily manipulated by Russ Cargill into authorizing the destruction of Springfield. When Cargill warns of the possibility of a public backlash after learning of Springfield becoming a no man's land, Schwarzenegger laments returning to making family comedies.
Colin (Tress MacNeille) is a young environmentalist who has moved to Springfield from Ireland. He falls in love with Lisa, and the film ends with them holding hands. Lisa initially suspects that Colin's dad is Bono from U2, since Colin is Irish and states his father is a musician; Colin repeatedly says that his father is not Bono. When asked if he plays instruments, he modestly replies, "Just piano, guitar, trumpet, drums, and bass." During Trappucino, Lisa is forced to leave Colin behind. He writes a song for Lisa, but because she cannot hear him through the dome, he writes the sheet music on the dome's surface. At the end of the film Colin and Lisa go on a date. Note 2