Even though The Ned Zone was on Lenny's birthday, we do not see him, but he is mentioned. Additionally, this segment also has Carl without Lenny.
The 'In The Belly Of The Boss' segment refers to Fantastic Voyage. Marge's line 'I must admit, they know where to stop' in reference to the antibodies is a reference to the film in which Raquel Welch's clothing is eaten away at in suspiciously just the right places.
This is the third Halloween episode where the Simpsons break the fourth wall. After finding out that the entire family cannot be saved, Lisa says "This is the worst Halloween horror we've ever faced!" The last time the Simpsons broke the fourth wall was in Treehouse of Horror XIV, in which Homer wishes he "was Death again." The first time was back in Treehouse of Horror V, in which Willie comments (briefly) on himself getting axed in the back in all three segments, "Ach, I'm bad at this."
This is the second Simpsons episode to parody Perfect Strangers. The first was in "Barting Over."
Homer and Burns become attached to one another again, the first time being "If I Only Had a Brain," the final vignette of Treehouse of Horror II.
"The Ned Zone" is the first segment of this episode. In Treehouse Of Horror II, There was a story with a similar name, "The Bart Zone", which was also a second segment and revolved around a character gaining extrasensory perception.
While in the Curio shop own by the Comic Book Guy you can see he has on his desk the monkey paw from one of the previous halloween specials.
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 porstitute 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.
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."
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.
Four Weddings and a Funeral: The name of "Four Beheadings and a Funeral" is taken from the name of this movie.
Sherlock Holmes: Lisa's character in "Four Beheadings and a Funeral" resembles Sherlock Holmes, and Bart's character is reminiscent of Dr. Watson.
Jack the Ripper: Jack the Ripper is referenced in "Four Beheadings and a Funeral."
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.
Fantastic Voyage: "In the Belly of the Boss" is a parody of this 1966 classic science-fiction movie. Homer even utters the title in regard to Marge's skimpy outfit.
Happiness is a warm Poppy: "Happiness is a warm Poppy" is a reference to 1968 The Beatles song "Happiness is a warm gun" or possibly "Happiness is a warm Puppy" from Peanuts.
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.
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.
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.
When Chief Wiggum throws Homer the gun the window is still closed.
Mr.Burn's underwear design changes from briefs to boxers.