This is the last Treehouse of Horror episode to double as a season premiere.
Previous episode references
"Treehouse of Horror V" and "XIV": The fourth wall is broken. (Willie: (after getting himself axed in the back while trying to save the day in all three segments) "Ach, I'm bad at this."/Homer: "I wish I was death again"/Lisa: "This is the worst Halloween horror we've ever faced!")
"Treehouse of Horror VI": Homer ends up in an unusual location and finds good luck (Homer gets sucked into the real world and goes to an erotic cake shop/Homer ends up in Heaven and God Himself gives Homer his frisbee back).
"Treehouse of Horror VIII": Springfield gets blown up, Bart gets swallowed by a fantastic creature but gets out unharmed and Bart's head shrinks.
"Saturdays of Thunder": A Simpson (Bart/Homer) pays attention to every word of a character's (Martin/Ned) warning except for the crucial "don't".
"'The Blunder Years": Homer's scream has been re-used as the Gracie Films and 20th Century Fox Television logos play.
This is the first Treehouse of Horror episode and the third Simpsons episode to be given an 'M' rating in Australia, instead of the usual PG and, as such, its screening on Channel 10 was pushed back to 8.30pm from 7.30pm (this episode was given an M rating for brutal violence against women [the prostitute murders] and references to opium smoking [including a scene of a child—Ralph—smoking opium]). The first Simpsons episode to have a 'M' rating in Australia was "Natural Born Kissers" for sexual situations and brief nudity and then "Weekend at Burnsie's" for references to marijuana smoking and scenes of animals abusing Homer.
Perfect Strangers: In the opening segment, the closing credits appear over freeze frames from the episode, with the song "Nothing's Gonna Stop Me Now" playing behind them. This is done in the style of the 1980s sitcom "Perfect Strangers."
Gypsy: Homer's comment, "Everything's coming up Homer!" is a reference to the song "Everything's Coming Up Roses" from the Broadway musical Gypsy.
The Dead Zone: The title and general concept of "The Ned Zone" is taken from this 1979 Stephen King novel, which has been adapted into a 1983 movie starring Christopher Walken and, in 2002, a serial drama starring Anthony Michael Hall. In all three, a mild-mannered man experiences psychic visions after receiving a blow to the head and going into a coma.
That's So Raven: Ned can see the future, but never gets it right. The tight closeups on Ned's eye and the sound effect when he has a vision are also similar to the ones used for Raven's visions.
Minority Report: Both Ned and the main character of this film are exposed to a vision of the future in which they murder someone unpremeditatedly.
The Twilight Zone: The Ned Zone is reminiscent of a Twilight Zone episode called "The Purple Testament." The title card is also animated in TZ style.
The Bridge on the River Kwai: The scene where Homer falls onto the core destruct button is very similar to the scene where Colonel Nicholson falls onto the plunger.
Four Weddings and a Funeral: The name of "Four Beheadings and a Funeral" is taken from the name of this 1994 romantic comedy film.
Pygmalion: In the second segment, Marge is portrayed as a "proper-Cockney flower girl" which is a reference to Eliza Dolittle the main leading character of the English Play.
From Hell: Four Beheadings and a Funeral is based on this 2001 horror mystery film since the film itself is based on the Jack the Ripper murders.
Sherlock Holmes: Lisa's character in "Four Beheadings and a Funeral" resembles Sherlock Holmes, and Bart's character is reminiscent of Dr. Watson.
China: In "Four Beheadings and a Funeral," Mr. Burns has unusually long fingernails. This is a reference to ancient China, when very rich or important people grew their fingernails long as a sign that they had no need to work in the fields, like the poor did. Also, the opium he is so fond of originated there.
A Christmas Carol: C. Ebezener Burns's name is a reference to Mr. Burns's title of C. Montgomery Burns and Ebenezer Scrooge, the character of the story.
The Adventures of Little Nemo: The ending segment of "Four Beheadings and a Funeral" with Ralph and Chief Wiggum flying on a bed from the novel and animated film The Adventures of Little Nemo.
Fantastic Voyage: "In the Belly of the Boss" is a parody of this 1966 science fiction film. Sure, Homer even utters the title when he regard to Marge's skimpy outfit.
In the Belly of the Beast: The name of "In the Belly of the Boss" is taken from the name of this book.
Happiness is a warm Poppy: "Happiness is a warm Poppy" is a reference to "Happiness is a warm Puppy" from Peanuts.
Jack the Ripper: In "Four Beheadings and a Funeral" the whole story about the police officer being the killer is an actual Jack the Ripper theory. The theory was that a former officer of Scotland Yard was the Ripper, but was proven false because he suffered strokes before the murders occurred.
Firefly: Co-Executive Producer Don Payne is credited as Don "Reavers" Payne. "Reavers" are the race of cannibals that menace the edge of the solar system in television series Firefly.
Animaniacs: The joke where Lou and Eddie mistake "Prince" for "prints" is similar to a controversial joke in the Animaniacs, where Yakko (as a detective) asks Dot to search for prints, only for her to come back later with the singer Prince.
The Ned Zone
The number of buttons on Dr. Hibbert's coat changes from four to three and back to four again in the scene where he says "Alright, but I swear by God, this is the very last time."
Flanders wakes up in the hospital without his glasses. After he shakes Dr. Hibbert's hand and foresees his death (when the camera zooms in towards his eye), he is wearing them. Then, when they zoom out, he is not wearing them anymore.
When Flanders foresees Dr. Hibbert's death, he is restrained to the bed, but when Hibbert dies he is by the window.
When Chief Wiggum throws Homer the gun, the window is still closed.
Homer's bullet wounds are seen throughout the scene staggering around the sealed chamber, but they vanish when his tongue falls onto the Core Destruct button.
Four Beheadings and a Funeral
When Selma dies her tongue moves up when the sword is pulled out but it would be impossible as the tongue would have been down instead of up.
Despite the title, no funeral took place. Nor was anyone beheaded.
In the Belly of the Boss
When Marge looks over to Maggie's empty stroller there are unclasped straps where there were none before.
When Marge points out that the white blood cells are eating her clothes, she is stripped to her undergarments. However, when she later exits the ship she is seen in the clothing she was wearing beforehand. It's possible there was another suit on the ship.
Mr. Burn's underwear design changes from briefs to boxers.
Mr. Burns points out that even Frink's pen can hurt him, but Homer's body couldn't cut up Mr. Burns' Skin.