When Father Malone first discovers the journal he glances at the title page, then flips to an open page of text that is partially blocked, and seen only for a split second. The visible portion reads (with spelling errors): "[something something] my college education to work writing dumb shit in this fucking movies props, Being one. It's time to bring in the the words guide or the big tits, tatoos and shaved beavers. I know horny [blocked]s would go [blocked] some of that".
After a rough cut editing the movie appeared to be much too short for a theatrical release (about 80 minutes), John Carpenter subsequently added the prologue with the Old Captain telling ghost stories to fascinated children by a campfire.
While driving to the lighthouse, Stevie flips around the radio dial, and a broadcast confirming a search for the ship The Sea Grass is heard. The voice mentions "a sweep south of Waitely Point and Arkham Reef". Both Arkham Reef and the surname "Waitely" are references to writer H.P. Lovecraft, as he used both repeatedly in his stories. Carpenter is an admitted Lovecraft fan.
At one point during the movie, Tom Atkins' character mentions Bodega Bay. That is the scene of another horror movie, The Birds (1963). When Tippi Hedren's character pulls into town, all hell starts to happen. In this movie, when Jamie Lee Curtis' character pulls into town, all hell starts to break loose.
Blake, the lead ghost, was played by makeup specialist Rob Bottin. When Bottin asked for the job, John Carpenter asked him to "stand up". Bottin then expected Carpenter to say, "...and get out!" When Carpenter saw that Bottin was a very large man, which was needed for the Blake character, he was hired.
John Houseman's opening monologue, which is supposed to transpire over a course of five minutes (from 11:55 to 12:00 midnight) is, in fact, only 2 minutes and 25 seconds long from the moment he mentions it is 11:55 to the moment the bells ring in the background, signaling midnight. It has been incorrectly noted in the past that this opening monologue is exactly five minutes long.
The quote "like an albatross around the neck" can be heard on the record cassette in the lighthouse where Stevie Wayne (Adrienne Barbeau) works, just before that a wooden piece with the word "Dane" explodes when the quote "6 Must Die" appears magically written in it. The quote about the albatross belongs to The Rime of the Ancient Mariner, created by Samuel Taylor Coleridge and published in 1798.
John Carpenter has stated two inspirations for the film, both of which are related to Great Britain. The first was the British film The Crawling Eye (1958) which dealt with monsters hiding in the clouds. He also stated that he and his co-writer/producer, Debra Hill, were inspired by a trip to Stonehenge, the ancient monument in South West England, which was covered in fog during their visit.
The sword that Blake carries is a Pattern 1796 Light Cavalry Sabre with an iron scabbard, produced between 1796 and 1821. Designed by Brigade Major John Le Marchant and Birmingham sword cutler Henry Osborn.
Although this was essentially a low budget independent film, John Carpenter chose to shoot the movie in anamorphic widescreen Panavision. This decision gave the film a grander feel for the viewer so it didn't seem like a low budget horror film.
As Stevie calls out the progress of the fog through town over the radio, she mentions Russelville road and Smallhouse road. These are two prominent streets in Bowling Green, Kentucky, where John Carpenter spent time growing up.
The journal's last page that Father Malone (Hal Holbrook) read when he finds it in the wall says: "April 30 - Midnight 'til one belong to the dead. Good Lord deliver us". It's a reference for Walpurgis Night, a pagan feast which happens in the night between April 30 and May 1.
Characters Nick Castle, Dan O'Bannon, Tommy Wallace are all named after Carpenter's real-life collaborators from his previous films. Mrs Kobritz was named after Richard Kobritz, Carpenter's producer on Someone's Watching Me! (1978).
The trivia items below may give away important plot points.
Extensive re-shoots were done after the first screening when director and studio executives decided that the movie wasn't scary enough. Additional scenes shot include close-ups of death scenes (specifically stab wounds), the scene with Jamie Lee Curtis and the walking corpse in the morgue, and the finale with Adrienne Barbeau on top of the lighthouse.
Adrienne Barbeau' has one scene with her son, and a climactic showdown with two of the ghosts. Other than that, all of her scenes were by herself with no on-screen interaction with any other characters.
In the last scene where Stevie is on top of the lighthouse and the fog slowly disappears, the crew realized they wouldn't be able to get the fog to roll out, so they had Adrienne Barbeau do the scene in reverse.
In the final scene at the church, Nick has Andy stand back and hide. On the wall behind Andy is a brick inscribed "H. Hawks." This is undoubtedly a reference to John Carpenter's favorite director Howard Hawks.