In-show deaths

Even though The Simpsons primarily maintains the status quo, throughout the run of the series, several characters, both recurring and one-time, have died. Additionally, many characters have been jokingly killed off during the Treehouse of Horror episodes.

Flashbacks

 * Uncle Hubert, died in the The Simpsons shorts episode "The Funeral".
 * Clancy Bouvier (1928-1977), in "Jazzy and the Pussycats" Marge says that he died shortly after she married Homer.
 * Snowball I (1988-1990), (died after being hit by a car, being driven by Clovis Quimby. The death is first mentioned in "Simpsons Roasting on an Open Fire" with Clovis Quimby being mentioned as the killer in "Treehouse of Horror III".
 * Orville Simpson , (seen in Heaven by Bart in "Bart Gets Hit by a Car".
 * Milton Haas, died from a hernia while carrying the crate of stolen Nazi paintings out of the German castle.
 * Sheldon Skinner, Arnie Gumble, Iggy Wiggum, Etch Westgrin and Giff McDonald, killed during the 1979 Veterans Day float disaster.
 * Soilder: eaten by an elephant during the Vietnam War despite Skinner's warning in Skinner's Sense of Snow.
 * C. W. McAllister died on the Murderhorn mountain in 1928, presumably from altitude sickness as his oxygen was stolen. Abraham Simpson has taken a bite out of his arm. His body was only found in "King of the Hill".
 * Waylon Smithers, Sr., died of radiation poisoning. When he was younger Homer Simpson discovered his body, presumably a while after his death as it had quite substaintually decayed. Homer had flashbacks of the event when he was hypnotised in "The Blunder Years". Mr. Burns later showed the Simpson family, as well as Chief Wiggum and Waylon Smither Jr., the footage of his death. Showing that he had died saving Springfield.
 * Asa Glick, held a granade in his hand to long & was blown up.
 * Johnny, killed by the Vietnamese as seen in a flashback in "I Love Lisa".
 * Child actor playing Alfalfa on Our Gang, beaten to death by Moe Szyslak as seen in a flashback in "Radioactive Man".

Season 1

 * None 

Season 2

 * Beatrice Simmons, died of a burst ventricle "Old Money", although Abraham Simpson says that it was actually a "broken heart", after he was unable to attend her birthday party.

Season 3

 * Snuffy, Lisa's pet hamster. She recites a poem about his death in "Stark Raving Dad".
 * Stinky and Wrinkles, Bart kills the school fish with a yo-yo, whilst trying the 'Plucking the pickle' trick.
 * Hamster, died on operating table in "Dog of Death".

Season 4

 * Aunt Gladys Gurney, died in "Selma's Choice".
 * Numerous people apparently fall to their deaths after riding on an escalator to nowhere in "Marge vs. the Monorail".

Season 5

 * Boris Simpson, left the Simpsons family his house when he died in "Homer Loves Flanders".
 * Man, head exploded by the rising sound effects of the THX cinema.

Season 6

 * Bleeding Gums Murphy, died in hospital from illness in "'Round Springfield".
 * Superdude, the school gerbil, crushed by his water bottle in "Who Shot Mr. Burns? (Part One)".
 * Dr. Marvin Monroe, It is unknown whether Marvin Monroe is actually dead. In "Who Shot Mr. Burns? (Part Two)", the hospital Burns attends is called The Marvin Monroe Memorial Hospital, and since that, his gravestone has been seen. Most prominently, in The Simpsons 138th Episode Spectacular one of the trivia questions asked was "Which two popular characters have died in the past year?" With the answer being, "If you said Bleeding Gums Murphy and Dr. Marvin Monroe you were wrong, they were never popular," indicating he is dead. However, Marvin Monroe re-appeared ten years later in the episode "Diatribe of a Mad Housewife", saying that he has been "very sick". If his death had taken place, it is estimated to have happened some time during Season Six.
 * A Man falls into in a sea of lava reaching for a pay phone at answer Bart's call in "Bart vs. Australia".

Season 7

 * Presumbaly anyone in Shelbyville when the Springfieldians knocked Mr. Burns' sundial on Shelbyville in Who Shot Mr. Burns? (Part Two).
 * Hortense Simpson, died sometime before "Bart the Fink" and left the Simpsons $100 each.
 * Asa Phelps, died in "Raging Abe Simpson and His Grumbling Grandson in "The Curse of the Flying Hellfish"", leaving Abraham Simpson and Charles Montgomery Burns as the last two surviving members of their army unit, and the last two in line to inherit the stolen Nazi paintings.
 * Mr. Estes, a publications advisor, died and left Lisa Simpson in charge of the school year book, sometime before the episode "Summer of 4 Ft. 2".

Season 8

 * James Bont, a James Bond parody, was shot to death by Hank Scorpio's guards in "You Only Move Twice".
 * Convicted Man, was about to be executed in Springfield State Prison's electric chair when Hurricane Barbara lifted the roof off the prison and pulled him into the air, ostensibly to safety. He subsequently landed on some power lines and was electrocuted, in "Hurricane Neddy".
 * Frank Ormand, the man who gave Marge Simpson the idea to begin a pretzel business. Died in a car crash in "The Twisted World of Marge Simpson".
 * The executor of Frank Ormand's will, died in a car crash along with Frank Ormand, in "The Twisted World of Marge Simpson".
 * Shary Bobbins, died after being sucked into a jet engine in "Simpsoncalifragilisticexpiala(Annoyed Grunt)cious".
 * Frank Grimes, died of electrocution after touching some cables marked "Extremely High Voltage" without safety gloves, whilst impersonating Homer Simpson in "Homer's Enemy". He was alluded to later on in the series in the episode "Natural Born Kissers" when Homer found a program from his funeral in a suit jacket pocket, as well as in "The Great Louse Detective" when Frank Grimes's son tries to murder Homer to avenge his father's death.
 * The Fish in Disco Stu's shoes, died presumably because of using up all of the oxygen in their water, or from constant trauma, considering they were in Aquariums in Disco Stu's shoes. Stu explained that he "couldn't get them out of there".

Season 9

 * Captain Tenille, presumably died when Homer Simpson torpedoed him out of a submarine in "Simpson Tide".

Season 10

 * Mr. Pinchy, Homer Simpson's pet lobster, was accidentally cooked to death when the bath water he was in was too hot. An extremely upset Homer ate Mr. Pinchy later at dinner in "Lisa Gets an "A"".
 * Red Barclay, died in "Maximum Homerdrive" after a beef-eating contest. Dr. Hibbert, a partner of the stakehouse, says he died of beef poisoning, although it was "probably from some other restaurant".
 * Mother bird, Bart Simpson accidentally shots the bird with Nelson Muntz's BB gun. The gun had a crocked sight, which meant that despite the fact that Bart was aiming away from the bird, he still killed it. Bart had to look after her eggs, in "Bart the Mother".

Season 11

 * Maude Flanders, died in "Alone Again, Natura-Diddily" when she was knocked off a racetrack grandstand by t-shirts shot from cannons. She was killed off due to problems with her voice actress Maggie Roswell. Maude's death is considered to be the most show-changing death, and affected Ned Flanders in several episodes after the incident.
 * Cornelius Chapman, the only man in Springfield older than Mr. Burns (at 108 years old). He died onstage from a heart attack after a kiss on the cheek from Britney Spears. Fittingly enough, he was receiving an award for Springfield's Oldest Man in "The Mansion Family".
 * The Laramie Cigarette Team died when the helicopter exploded at the hands of a Tomacco addicted sheep (who was the only survivor.)

Season 12

 * Man having operation, died when a tennis ball landed in his open chest in "Tennis the Menace", after Dr. Hibbert decided to operate on him outside.

Season 13

 * Professor at Swigmore University, was dying of cancer, in "Homer the Moe" he kills himself by walking in to a lake. He later appears as a ghost.

Season 14

 * Congressman Horace Wilcox, died of a stroke in "Mr. Spritz Goes to Washington".

Season 15

 * Lawyer, died when Homer drove over him in "My Mother the Carjacker".
 * Diver, got electrocuted in "The Fat and the Furriest".
 * Fishes, got electrocuted in "The Fat And The Furriest".
 * Snowball II, Got rammed by a truck in "I, D'oh-Bot".
 * Snowball III, Drowned in the fishbowl while trying to catch fish in "I, D'oh-Bot".
 * Coltrane, a.k.a. Snowball IV, jumped out of Lisa's window while hearing John Coltrane's music in "I, D'oh-Bot".
 * Nuclear Inspector, after being rammed by Homer's car in "Diatribe of a Mad Housewife".
 * Presumably everyone within the Dayton Arms Hotel, when it was obliterated on screen (all the way to the basement) in "Catch 'Em if You Can".
 * Presumably everyone in a nearby bus in addition to everyone in the Dayton Arms Hotel the twister killed a bus is shown nearby trying to drive away but getting picked up and being thrown away.Vlcsnap-2012-12-17-17h53m08s13.png
 * Elmo, hung himself in "Bart-Mangled Banner", after being wrongly imprisoned at the Ronald Reagan Reeducation Center.
 * Mr. Teeny I, II and III, Krusty remarks that he hasn't been this sad since Mr Teeny III died in "Fraudcast News".

Season 16

 * Health Inspector Frankie, died when eating one of Moe Szyslak's pickled eggs in "Mommie Beerest".
 * Los Lobos, along with several other unnamed celebrities, died after falling out of a blimp.
 * James Caan, ambushed and gunned down by hillbillies at a toll booth in "All's Fair in Oven War".

Season 17

 * Buried Man, a man who was buried alive by Gravedigger Billy in "The Girl Who Slept Too Little ".
 * Fred Kanneke, Chief Wiggum's brother-in-law who was given euthanasia in Million Dollar Abie.

Season 18

 * The Callibricis, the rival gang of Fat Tony's, died of food poisoning.
 * The Callibricis' Goons, died in a car explosion.
 * Amber Simpson, Homer's Vegas wife died of an overdose whilst in front of a "Do not stand up on the rollercoaster" sign.
 * Max, an ice cream truck driver. Died whilst giving Homer change for a $100.
 * Diver, drowned, when Nelson stole his equipment.
 * Most of the population of Shelbyville is apparently killed when an atomic bomb detonates there in "24 Minutes".

Season 19

 * People Reviewing Sundance Films, died from loss of breath in "Any Given Sundance".
 * Mona Simpson, dies of old age in "Mona Leaves-a".

The Simpsons Movie

 * Crushed Person, crushed by the dome as it was being installed over Springfield, killing him.
 * Dr Nick Riviera, crushed by a large shard of the dome when it was destroyed.
 * Green Day, killed when the boat they were playing on flipped over. The Springfield residents later pray for them in church.
 * Russ Cargill, presumbaly killed when Maggie dropped a boulder on his head.

Season 20

 * Mrs. Gumble, died sometime before "Double, Double, Boy in Trouble".

Season 21

 * Gypsy in the couch gag for 'Boy Meets Curl' She reads Grampa's Fortune of Death so he turns it to her causing her to insantly die.
 * Bluella, died in "The Squirt and the Whale" after she was washed up on the shore of Springfield.

Season 22

 * Raymond Bird, eaten by Santa's Little Helper in "How Munched Is that Birdie in the Window?"
 * Pa, died at some point before "How Munched Is that Birdie in the Window?"
 * Fat Tony dies of a heart attack in "Donnie Fatso" and replaced by his cousin Fit Tony.

Season 23

 * Victor, Wayne Slater threw an icepick at his throat in "The Falcon and the D'ohman"
 * Victor's wife, accidently killed by Wayne Slater in "The Falcon and the D'ohman". Victor once held a large party in his mansion, with many guests in a large ballroom but Wayne Slater gatecrashed the party which lead to gunfights. Victor's wife appears and Wayne hits a man's gun out of his hands. It then fires and hits Victor's wife.
 * Alice Glick killed by a rogue seal robot in "Replaceable You".

Season 24

 * Steve Mobbs died sometime before "A Tree Grows in Springfield".

Future episodes

 * Homer Simpson, dies 50 years later in Barting Over.
 * Homer and Marge Simpson, become ghosts 60 years later in The Boys of Bummer.
 * Bart Simpson, pulled apart by bulldozers, as revealed 1000 years later in The Father, the Son and the Holy Guest Star.
 * Sanjay Nahasapeemapetilon and Edna Krabappel, revealed to have died sometime before 30 years later in Holidays of Future Passed.

Fictional characters
Itchy and Scratchy always get killed (mostly Scratchy) in their episodes.

Season 8

 * Poochie, died on the way back to his home planet during an episode of the Itchy & Scratchy Show in "The Itchy & Scratchy & Poochie Show". He was killed off due to immense unpopularity. However, he still appears as a background character from time to time, so he may not actually be dead.

Season 14

 * Eric Cartman, Head cut of by O.J Simpson in A South Park Episode Bart & Milhouse were watching.
 * Farty the Crippled Robot, head cut of By O.J Simpson in a South Park episode Bart & Milhouse were watching.

Season 15

 * Mr. O'Bannon, a charecter in the Video Game Hockey Dad killed in the fight. played by Milhouse.

Season 20

 * The wicked queen died brutally by woodland animals in Four Great Women and a Manicure.

Treehouse of Horror deaths
Note: Treehouse of Horror deaths are kept separate due to the nature of Treehouse of Horror episodes. Treehouse of Horror episodes aren't continuous with the rest of the series, giving the writers the possibility of killing off important characters without having to create a replacement or write them out of the series (e.g. in Treehouse of Horror XV, Homer obliterates Springfield, but the series continues on.)

Treehouse of Horror

 * Marge Simpson (as Lenore), referred to as "Lost Lenore" in "The Raven" segment of an unknown cause.

Treehouse of Horror II

 * No deaths.

Treehouse of Horror III

 * Lenny Leonard, eaten by King Homer.
 * Waylon Smithers, eaten by King Homer.
 * Shirley Temple, eaten by King Homer.
 * Journalist, crushed by King Homer.
 * Clancy Bouvier, eaten by King Homer.
 * Numerous zombies (Ned Flanders, Albert Einstein, William Shakespeare, Edna Krabappel, and George Washington to name a few), killed mainly by Homer when zombies attack Springfield.

Treehouse of Horror IV

 * Groundskeeper Willie's mule, Willie comments that he had to put seventeen bullets in him.
 * Ned Flanders, killed by a gremlin through decapitation. (Although he was still able to speak.)
 * Bart Simpson, bitten by Mr. Burns who was a vampire, turned into a vampire.
 * Charles Montgomery Burns (Vampire), died of a stake through heart by Homer after first staking his crotch.

Treehouse of Horror V
Note that the people killed in the third segment didn't die because it was in Bart's nightmare.
 * Moe Syzlak, hung.
 * Patty and Selma Bouvier, burned at the stake by Reverend Lovejoy.
 * Mrs. Krabappel, Groundskeeper Willie, Chief Wiggum, and Principal Skinner, heads chopped off by Bart.
 * Groundskeeper Willie, stabbed in the back with an axe in each of the three mini-episodes, all while trying to help the main character of the episode. In the third death he replies that he's "bad at this."
 * Patty Bouvier, revealed to have died in an alternate universe. The cause of her death, however, is not mentioned.
 * Selma Bouvier, revealed to have died in an alternate universe. The cause of her death, however, is not mentioned.
 * Mosquito, squashed by Homer.
 * Walking fish, sat on by Homer.
 * T-Rex and other dinosaurs, dies from a spreading cold when Homer sneezed at the T-Rex.
 * A big dragonfly, beaten to death by Homer.
 * Compy, stepped on by Homer.
 * Jimbo Jones, cooked by Skinner and turned into Sloppy Jimbos
 * Üter, cooked by Skinner and turned into Uterbraten
 * Milhouse Van Houten, Bart Simpson and Lisa Simpson, fell in a giant blender.

Treehouse of Horror VI

 * Martin Prince, strangled to death by Willie.
 * Otto Mann and a school bus of students(including Sherri, Terri, Ralph and Richard), unknown if they got killed by a billboard of the Devil come to life.
 * Captain of the High School Basketball team, shot by Chief Wiggum who thought he was a monster.

Treehouse of Horror VII

 * Bill Clinton, ejected into space, completely naked.
 * Bob Dole, ejected into space, completely naked.

Treehouse of Horror VIII

 * FOX Censor, stabbed to death.
 * Kent Brockman, Mayor Quimby, Herman, Comic Book Guy, Krusty the Clown and Kirk Van Houten, killed by a nuclear neutron bomb. Others including, Lenny, Carl, Sideshow Mel, Mr. Burns, Dr. Hibbert, Ned Flanders, Chief Wiggum, Apu Nahasapeemapetilon, Waylon Smithers, Principal Skinner, Moe Szyslak, Groundskeeper Willie, and the Sea Captain were all mutated and later shot by Marge, Bart and Lisa.
 * Johnny and Edgar Winter, run over by Homer, who mistook them for mutants.
 * Agnes Skinner, Miss Hoover, and Luann Van Houten, burned alive.

Treehouse of Horror IX

 * Homer Simpson, hit by Marge Simpson's car.
 * Lisa Simpson, crashed into a wall on her bike.
 * Bart Simpson, accident on his skateboard.
 * Snake Jailbird, electrocuted in an electric chair.
 * Apu Nahasapeemapetilon, drowned in a Squishee machine by Homer Simpson
 * Moe Szyslak, Homer Simpson pulled his heart out with a corkscrew.
 * Poochie, hit by a police car driven by Itchy and Scratchy.
 * Jerry Springer, suffocated by Kang's tentacle, he was also possibly killed from a venomous bite of the alien/human hybrid Maggie Simpson.
 * Audience of the Jerry Springer show, zapped by laser gun.

Treehouse of Horror X

 * Lisa Simpson, disintegrated by an alien Maggie from Treehouse of Horror IX.
 * Ned Flanders, hit by a car. However, he reappeared as a zombie werewolf, so now he is undead.
 * Homer Simpson, possibly killed by werewolf Ned Flanders.
 * Comic Book Guy as The Collector, killed by Lucite.
 * Nelson Muntz, falls into copying machine.
 * Krusty the Klown, killed by a pace maker inside his stomach.
 * Homer Simpson, blown up after escaping the spaceship going into the sun, died because of no oxygen in space.
 * Bart Simpson, blown up after escaping the spaceship going into the sun, died because of no oxygen in space.
 * Celebrities on doomed spaceship, died when their spaceship flew into the sun.
 * Bernice Hibbert, Dr. Hibbert, Ned Flanders, Helen Lovejoy, Reverend Lovejoy, Abraham Simpson, Lenny, Carl, Kirk Van Houten, Ruth Powers, Captain McCallister, Snake, Miss Hoover, Crazy Old Jewish Man, Sideshow Mel, Lou, Eddie, Willie, Principal Skinner, Luann Van Houten, Mrs. Krabappel, Dr. Nick, Waylon Smithers, Otto, Comic Book Guy, Jasper, Bumblebee Man, Maude, Rod, Todd, Chief Wiggum, Legs, Martin Prince Sr., Martin Prince Jr., Arnie Pie, Brandine, Disco Stu, Agnes Skinner, Jimbo and Kearney, killed while all of the world's machines go haywire. Others, such as Lisa, Marge, Maggie and Professor Frink escaped on a spaceship going to Mars.

Treehouse of Horror XI

 * Homer Simpson, killed by an angry mob.
 * Bart Simpson, killed by an angry mob.
 * Marge Simpson, killed by an angry mob.
 * Abraham Simpson, killed by an angry mob.
 * Homer Simpson, choked to death on a piece of broccoli, twice.
 * Agnes Skinner, dropped to her death by Ghost Homer when he tries to do a good deed.
 * Simpson children, Bart and Lisa see their siblings skeletons.
 * Goldilocks, mauled by Daddy Bear, Mummy Bear and Baby Bear.
 * Suzanne the witch, burnt to death.
 * Lenny Leonard, killed by dolphins.
 * Captain McCallister, killed by dolphins.
 * Squeaky-Voiced Teen, killed by dolphins.
 * Kent Brockman, killed by dolphins.
 * Raphael, killed by dolphins.
 * Abraham Simpson, eaten by a dolphin, though a deleted scene shows him bursting out of the dolphin and joining in Springfield's battle against the dolphins.
 * Groundskeeper Willie, killed by dolphins.
 * Krusty the Clown, drowned in the sea.
 * Chief Wiggum, Lou, Eddie, Moe, Cletus, Brandine, Patty, Selma, Reverend Lovejoy, Helen Lovejoy, Disco Stu, Hans Moleman, Herman, Comic Book Guy, Mrs. Krabappel, Agnes Skinner, Principal Skinner, Luann Van Houten, Apu, Mr. Burns, Smithers, Superintendent Chalmers, Lunchlady Doris, Sarah Wiggum, Professor Frink, Mr Largo, Mayor Quimby, Ralph, Sam, Larry, Legs, Akira, Comic Book Guy, killed during dolphin battle. Others, such as Kirk Van Houten, Ned, Rod, Todd, Barney, Old Jewish Man, Dr. Hibbert, Bernice Hibbert, Bumblebee Man, Sherri, Terri, Jacques, Database, Kearney, and The Simpsons survived, but had to live out on the ocean.

Treehouse of Horror XII

 * Waylon Smithers, electrocuted.
 * Lenny Leonard, crushed and killed by a helicopter.
 * Carl Carlson, crushed and killed by a helicopter.
 * Moe Syzlak, drowned in a pickled egg jar
 * Bart Simpson, drowned himself in his cereal.
 * Ralph Wiggum, magical energy absorbed by Count Montymort.
 * Count Montymort, stabbed in enchanted shin (the source of his power) by Bart Simpson and Slithers eats him.

Treehouse of Horror XIII

 * Homer clone, electrocuted.
 * Ned Flanders, decapitated with a chainsaw by Homer clone.
 * 3 Homer clones that knew the way home, shot by Homer.
 * Gil Gunderson, killed by Homer clones, although he was still moving and speaking.
 * Homer clones, fall off a cliff.
 * Homer Simpson, falls off a cliff.
 * Zombies, shot.
 * Future Homer Simpson, shot by Moe.
 * Professor Frink, eaten after being turned into a turkey.

Treehouse of Horror XIV

 * Bart and Lisa, suffocated in a rug.
 * Homer Simpson, shot by Marge.
 * Grim Reaper, murdered by Homer with a bowling ball.
 * Homeless Guy, killed by Homer the Grim Reaper.
 * Jasper, killed by Homer the Grim Reaper.
 * Thirteen men (including Kirk Van Houten, Reverend Lovejoy and Hans Moleman) and three women (including the Queen), killed during a ball game (all by Homer, except the Queen who got hit by a baseball).
 * Patty Bouvier, killed by Homer instead of Marge.
 * Ned Flanders, killed by Professor John Frink Sr after he rips out his heart.
 * Seymour Skinner, killed by Professor John Frink Sr. after he rips out his spine.
 * 5 scientists,? brains removed by? by Professor John Frink Sr.
 * Professor John Frink Sr., died form a calculated kick to the groin from Professor John Frink Jr.
 * Martin Prince, died, or was seriously injured while being attacked by the angry mob.

Treehouse of Horror XV

 * The Simpson family (except for Bart), cooked by Kang and Kodos.
 * Dr. Hibbert, falls out of a window.
 * Hans Moleman, dropped down a sewer and devoured by crocodiles.
 * Homer Simpson, shot by Ned thrice.
 * Marge, Ned, Bart, Lisa, Chief Wiggum, Carl and Maggie, killed when Springfield is blown up by a Core Destruct Button.
 * Prostitute, killed by Clancy Wiggum.
 * Ned, Todd and Rod Flanders, their heads hang in Comic Book Guy's shop.
 * Comic Book Guy, killed by Clancy Wiggum.
 * Selma Bouvier, killed by Clancy Wiggum.
 * It should be noted that the last four deaths technically did not occur, as they were all part of Ralph Wiggum's dream.

Treehouse of Horror XVI

 * David, sliced in half by Bart.
 * Lenny, Carl, Barney, Sideshow Mel, Mr. Largo, Dr. Nick, Dr. Hibbert, Principal Skinner, Groundskeeper Willie, Apu, Otto, Lou, Squeaky-Voiced Teen, Kirk Van Houten, Kent Brockman, Comic Book Guy, Blue Haired Lawyer, Krusty the Clown, Captain McAllister, all shot by Mr. Burns (note: Apu was killed twice when he got reincarnated as a rabbit but got trapped in a bear trap).
 * Moe and Chief Wiggum, impaled on a weather vane.
 * Professor Frink, eaten by Homer.
 * Mr. Burns and Smithers, hit on the head with a frying pan by Marge.
 * Disco Stu, arrow through the head. (a la Steve Martin)
 * Mayor Quimby, eaten by dogs.
 * Martin Prince, sprayed by Groundskeeper Willie.
 * Abraham Simpson, It is unclear as to whether he is killed or not, but it is likely he would be listed as dead after Dr. Hibbert (who had became a vampire) flew off into the night with him. Abraham said, "That's it, suck out the poison...Wait a minute...Ahhhhh!" Implying that he had either been turned into a vampire (which would technically make him undead) or had been killed due to blood loss.

Treehouse of Horror XVII

 * Moe Szyslak, killed by an iron maiden.
 * Snowball V, eaten by Homer Simpson.
 * Squeaky-Voiced Teen, eaten by Homer.
 * Üter, eaten by Homer.
 * German People at Oktoberfest, eaten by Homer.
 * Fat Tony, eaten by Homer.
 * Comic Book Guy, eaten by Homer.
 * People in Umpire School, eaten by Homer.
 * People from "The Facts of Life Reunion Tour", eaten by Homer.
 * Guys in Hawaiian shirt store, eaten by Homer.
 * People on a bus, eaten by Homer.
 * Ned Flanders, had his head bitten off by Homer.
 * Dr. Phil McGraw, eaten by Homer.
 * Homeless People, eaten by Homer.
 * 17th Century People, shot by the Golem of Prague in a flashback.
 * Audience members at Krusty's stand up show, shot by the Golem of Prague.
 * Jimbo, Dolph, and Kearney, die after the Golem switches their heads.
 * Principal Skinner, sliced in half by the Golem of Prague. (However, he still moved and talked before being put in a bag, but he is listed by Chief Wiggum as dead, so he is probably killed by the Golem.)
 * Barney Gumble, hit with a bat by Moe.
 * Lenny Leonard, shot by Homer, who thought he was an alien.
 * Disco Stu, shot by Homer, who thought he was an alien.
 * Captain McAllister, decapitated by Homer.
 * Clancy Wiggum, sucked dry by Kang and Kodos's spaceship.
 * Apu, Cletus, Kirk Van Houten, Jasper, Willie, Crazy Old Man, Ned, Mr. Largo, Carl, Abraham, Squeaky Voiced Teen, Reverend Lovejoy, Orson Welles, Otto, Homer, Marge, Mrs. Krabappel, Sherri, Terri, Martin, Wendell, Lewis, Milhouse, Bart, Nelson, Richard, Sam, Larry, Moe, Jimbo, Superintendent Chalmers, Luann Van Houten, Mayor Quimby, Helen Lovejoy, Professor Frink, Ned Flanders, Miss Hoover, Cookie Kwan, Lindsay Neagle, Sideshow Mel, Dr, Hibbert, Bernice Hibbert, Dr. Nick, Agnes Skinner, Ralph, Kearney, Database, Krusty, Lisa, Principal Skinner, Sarah Wiggum, Waylon Smithers, and Comic Book Guy, all killed in Kang and Kodos' invasion.

Treehouse of Horror XVIII

 * Three soldiers, killed by Kodos.
 * Various Rigellian IV Aliens - Killed by USA troops.
 * Kang is shot.
 * Kodos is suffocated.
 * Kent Brockman, killed by Marge.
 * Four men, Disco Stu and Captain MacAllister, accidentally shot by Homer.
 * Grampa, accidentally killed by Homer as he tries to kill Marge.
 * Principal Skinner, killed by Marge and Homer.
 * Groundskeeper Willie, killed by his killer tractor.
 * Dr. Hibbert, run down by a van.
 * Homer, killed when he is cut to pieces through his own hammock and his head turned to spaghetti.

Treehouse of Horror XIX

 * Homer, killed by voting booth when he gets sucked into it and shot out afterwards.
 * Grandpa Simpson, possibly died after passing out in the Simpson's front yard.
 * People On Plane, coughed out by Plane Robot onto runway.
 * Various People Throughout Springfield, probably killed during robot battle.(This includes Otto, since he was in that episode but was not seen later on at the end with the others, but it is uncertain if he died.)
 * Krusty the Clown, shredded by a woodchipper.
 * George Clooney, Prince, Neil Armstrong, and other celebrities, Killed by Homer (George Clooney fell in quicksand, prince was strangled with his guitar by Homer and stabbed, and Neil was hit and became unconscious from a flying golf club).
 * Several people at the party, shot by deceased celebrities that came down from heaven.
 * Chief Wiggum, Shot by the deceased Edward G. Robinson.
 * Homer, head blasted off by the deceased Krusty the Clown, eaten by the Grand Pumpkin.
 * Principal Skinner, killed by Grand Pumpkin.
 * Grand Pumpkin, killed by Tom Turkey.
 * 5 Students at the Party(including Richard, Lewis and Ralph), eaten by Tom Turkey.

Treehouse of Horror XX

 * Homer Simpson, head gets chopped off and it falls in the punch bowl at the party.
 * Miss Hoover, killed by Bart.
 * Principal Skinner, killed by Bart.
 * Bart Simpson, accidentally killed by Lisa with a knife.
 * Helen Lovejoy, shot by Marge.
 * Apu Nahasapeemapetilon, killed by munchers.
 * Rainier Wolfcastle, killed by munchers.
 * Moe Szyslak, presumbly killed when he was taken by munchers Lenny, Carl, and Barney.
 * Hans Moleman, ran over by car.
 * Squeaky-Voiced Teen, killed by muncher Kent Brockman.
 * Dr. Hibbert, killed by munchers.
 * Muncher Mr. Burns, killed by Homer.
 * Waylon Smithers, killed by Homer.
 * Doctor munchers, killed by Dr. Hibbert.

Treehouse of Horror XXI
- Milhouse, drowned. NOTE: The previous five deaths may not have happened for it is all in Maggie's Imagination.
 * Bart, beat to death by Homer with a tombstone.
 * Professor Frink, killed by aging himself with a DVR remote.
 * Chief Wiggum, squashed by a giant Knight piece.
 * Hans Moleman, died in a game of Clue.
 * Rod and Todd Flanders, squashed in a tumbling block game.
 * Cards, shot by Bart.
 * Bart and Milhouse(again) hung. (Debatable)
 * Seagull, poisoned, but was stabbed with a marlin thrown by Homer at the end.
 * Shark, Squid and other sea life, killed by fuel from the Rent-a-Dream.
 * Roger, harpooned by Homer
 * Albatross crew, various weapon's including - anchor, flare gun, blunt weapon By Homer covering up murder of Roger
 * Marge, poisoned herself because of the guilt of Homer killing the crew
 * Ned Flanders - cooked for dinner
 * Big Bird - killed by Count von Count
 * Count Dracula and Edmund (possibly) - Homer's blood which was filled with cholesterol
 * Homer - when a bat, could not fly (possibly)

Treehouse of Horror XXII

 * Charles Montgomery Burns, Snake Jailbird, Patty and Selma, Sideshow Bob, killed by Ned Flanders under Homer's order.
 * Homer choked by God.

Treehouse of Horror XXIII

 * Cat Lady, Luann Van Houten, Kirk Van Houten, Sam, Larry, Principal Skinner, Jasper, Cletus, Brandine, Ruth Powers, Martin Prince, Blue-Haired Lawyer, Kent Brockman, Bumblebee Man, Reverend Lovejoy, Mayor Quimby, Chief Wiggum, Patty, Selma, Marge, Lenny, Carl, Moe, Groundskeeper Willie, Bart, Jimbo, Dolph, Kearney, Nelson, Edna Krabappel and Professor Frink, all killed when Earth explodes after the 13th baktun.
 * Moe Syzlak, decapitated.
 * Homer Simpson, crushed by a giant foot.
 * Sideshow Mel, had his skeleton sucked away by the black hole.
 * Mayor Quimby, Professor Frink, Cookie Kwan, Lindsey Neagle, Dederick Tatum, Manjula, Ned Flanders, Edna Krabappel, Superintendent Chalmers, Patty, Selma, Otto, Dewey Largo, Bernice Hibbert, Dr. Hibbert, Milhouse, Lenny, Carl, Santa's Little Helper, Hans Moleman, Kent Brockman, Groundskeeper Willie, Dr. Nick, Lunchlady Doris, Bumblebee Man, Fit Fat Tony, Waylon Smithers, Mr. Burns, Reverend Lovejoy, Helen Lovejoy, Krusty, Chief Wiggum, Sarah Wiggum, Captain McAllister, Squeaky-Vocied Teen, Rich Texan, Gil Gunderson, Rich Texan, Snake, Blue-Haired Lawyer, Moe Syzlak, Kearney, Ranier Wolfcastle, Old Jewish Man, Ruth Powers, Agnes Skinner, Rod and Todd, all killed in a black hole.
 * Chief Wiggum, eaten by the devil and turned into a skeleton.
 * Scratchy, had his chest impaled on a faucet and had his blood poured out of it.