Deep Thought explains the significance of the number 42, at 42 minutes into the film.

Douglas Adams's head appears as a planet during Slartibartfast's tour of the galaxy.

The producers have stated that this film is not a literal translation of the books (just as the books were not a literal translation of the original radio show), but all of the new ideas and characters came from Douglas Adams himself. The hired writer simply came aboard to improve structure and make the screenplay more coherent.

Easter Egg: The DVD includes an "Improbability Drive" item on every menu. Clicking this leads to a random point in one of the bonus features. Used several times leads to a strange cartoon, which is the same one Deep Thought watches.

Belgium (which, according to the original radio series, is the most unspeakably rude word there is) can be heard in the movie three or so times.

The old lady sitting at the street side table oblivious to or uninterested in what's going on around her is Douglas Adams's mother. The director didn't give any acting directions to her or anybody else in the scene for what they were suppose to do, to simulate chaos, so she just sat there reading a newspaper.

According to the DVD commentary, the animators who created the animated Guide entries would occasionally sneak in hidden in-jokes into their animations that were deemed too inappropriate for a family film and had to be removed. One of these jokes which wasn't removed is an animation explaining the Babel fish and how a farmer becomes repulsed when he learns that a cow is somewhat aroused by being milked.

This film was in "Development Hell" for over fifteen years. At one point, Douglas Adams insisted it would be made "sometime before the last Trump". Just prior to his death, a deal was almost in place with Jay Roach directing and starring Hugh Laurie (Arthur), Jim Carrey (Zaphod Beeblebrox) and the late Nigel Hawthorne (Slartibartfast).

Arthur learns the Guide's sole entry for earth is "Harmless" and that the updated version was to be "Mostly Harmless"; this was filmed but didn't make the final cut (it is included as a bonus deleted scene on the DVD). It would have been seen when Arthur and Ford arrive on the Vogon ship.

The model of Marvin the Paranoid Android from the original The Hitchhiker's Guide to the Galaxy (1981) is waiting in line when Arthur, Ford, and Zaphod are trying to find the correct form to rescue Trillian.

When the Heart of Gold heads for Magrathea the Infinite Improbability Drive changes it into a bell, some cherries, a melon and a lemon - all common features on a slot-machine, emphasising the randomness of the process.

According to Douglas Adams' notes, he wanted the name of the character "Slartibartfast" to sound extremely rude, but still pass BBC's rules on what could be broadcast - he actually started with "Phartiphukborlz" and changed it, bit by bit, until it was acceptable.

The nightgown/bathrobe Arthur Dent wore was the most expensive and difficult of all costumes (including Zaphod's heads and Humma's eyes). The fabric had to be sewn on stage and was flown in from Turkey.

This is the ninth version of the "Hitchhiker's Guide". It has previously appeared as a radio series, two record albums, novels, a television series (The Hitchhiker's Guide to the Galaxy (1981)), a computer game, a stage show, a comic book, a video game (The Hitchhiker's Guide to the Galaxy (1984)) and a towel. (The game version is not, in fact, a video game, but was an Infocom "interactive fiction" {text only} game, plotted/scripted by Douglas Adams, programmed by Steve Meretzky, which has been available to play free on the BBC Radio 4 website since 2005.)

As the emergency escape pod crashes on Vogsphere, the sound made by it is the same as the plane from the end of "In the Flesh", the first track on Pink Floyd's album "The Wall". Douglas Adams was a personal friend of Floyd guitarist David Gilmour and even played at one of their shows.

Faint screams can be heard a moment before Mr. Prosser speaks. In the book, Mr. Prosser is a direct male-line descendant of Genghis Khan, the reason why he wears little fur hats and often hears a thousand hairy horsemen shouting in his head.

The movie was first optioned in 1982 by producers Ivan Reitman, Joe Medjuck and Michael C. Gross. Douglas Adams wrote three drafts for them per his contract. During this time, Medjuck and Gross were considering Bill Murray or Dan Aykroyd to play Ford Prefect, but then Aykroyd sent them his idea for Ghostbusters (1984) and they did that movie instead.

The car that Ford Prefect "introduces himself to" is actually a Ford Prefect, from whence Ford got his "Earth name". Despite being a Ford, the car was never manufactured or sold in the United States, but produced in Ireland, the UK, Malaysia and New Zealand, and sold in Europe, Asia and Australia between 1938 and 1959.

The names of all five books - Hitchhiker's Guide to the Galaxy, Restaurant at the End of the Universe, Life the Universe and Everything, So Long and Thanks for All the Fish, and Mostly Harmless - are each mentioned throughout the course of the movie. The last, however, is only in the Deleted Scenes.

The Vogon written language seen on their release forms as well as in a bilingual caption in the Magrathean video which says "Information Deleted", is actually a form of English. Pitman shorthand, once taught to hundreds of thousands of office-workers mainly in the British Commonwealth, is a series of straight and curved strokes meant to write down sounds much faster than regular writing. As discussed in a book about the movie, the Vogons use a slightly blocky but recognizable form of "Pitman 2000", the most recent version of Pitman shorthand published in 1970. It occurs in the Vogon release forms, posters on the wall which say "Fire Exit Escape Map" (over a hopelessly confusing maze of arrows with a spot at the center saying "You Are Here") and "Are you depressed? Destruction Therapy!"

In one shot, the Apple Mac logo is visible on the side of Deep Thought, the giant computer. Douglas Adams owned the first two Apple Macintosh computers delivered to the United Kingdom, while Stephen Fry (the voice of the Book) owned the third. Both men were/are keen advocates of the Mac - Douglas and Stephen were close personal friends.

The relevance of Sector ZZ9 is the fact that in the UK if a person has NFA (No fixed Abode (No place to live)) then the POSTCODE is recorded as ZZ99 3VZ, thus Both Trillian and Arthur come from Sector ZZ9 and thanks to the Vogons they are both of NFA.

The fancy dress party contains several references to Douglas Adams' 40th birthday party, which happened in 1992. At the real party, Adams introduced Darwinian Evolutionist Richard Dawkins to the future Mrs. Dawkins, actress Lalla Ward. In the film, Arthur is seen reading Dawkins' book, "The Selfish Gene", when he meets Tricia, who is dressed as Charles Darwin. Adams and Dawkins became very good friends after Adams received a fan letter from him.

The Hitchiker's Guide is a parody of "The Encyclopedia Galactica" from Isaac Asimov's Foundation novels.

John Malkovich's character, religious leader Humma Kavula, was created especially for the movie by Douglas Adams. He does not appear in any previous version of the story. However, the Jatravartids, of whom he is the spiritual leader, are mentioned in the books.

Several minutes into the credits, a final Guide entry is shown. This is the "careless words/problem of scale" entry, well known to fans of other incarnations of the Guide.

Some additional shots were filmed to fit in with Arthur waking up at the beginning. In one shot (included in an early trailer, but cut from the film, and not on the DVD), Arthur's identification as a BBC employee can be seen. The original Hitch Hiker's radio and TV versions were produced by the BBC.

The Heart of Gold bridge set had so many light bulbs that the bulbs could only run for eight minutes at a time to prevent the set from catching fire.

Shada, the prison "planetoid" of the Time Lords, can be seen in the background during the factory floor scene on Magrathea. Doctor Who: Shada (1992) was a Doctor Who (1963) story that Douglas Adams wrote but was never completed for television due to a strike at the BBC. Characters and settings from "Shada" appeared in Adams' novel "Dirk Gently's Holistic Detective Agency", which recycled ideas from his serial Doctor Who: City of Death: Part One (1979).

The passage of 10 October 2010 (10/10/10) publicized the fact that, 101010, a binary equivalent of the number 42, is the number that received considerable attention in popular culture because of its appearance in Douglas Adams' 'The Hitchhiker's Guide to the Galaxy' as the answer to "the Ultimate Question of Life, the Universe, and Everything".

Bill Murray, Robert Downey Jr. and Johnny Depp (a huge Douglas Adams fan) were also considered for the part of Zaphod Beeblebrox, along with Will Ferrell. But after Sam Rockwell's audition, director Garth Jennings immediately chose him.

A painting of Douglas Adams and his wife Jane Belson appears on the Heart of Gold. Other Adams cameos include a few handles on some cupboards in Humma Kavula's office being shaped like Adams' nose.

When Ford and Zaphod first greet each other on the Heart of Gold, Zaphod calls Ford "Ix" and then quickly corrects himself. In the novel, Ford is from planet Betelgeuse Seven, which was destroyed during the unspecified "Great Collapsing Hrung Disaster of Gal./Sid./Year 03758". "Ix" was a nickname that Ford's childhood schoolmates gave him, which, according to the book, translates as "boy who is not able satisfactorily to explain what a Hrung is, nor why it should choose to collapse on Betelgeuse Seven."

Sam Rockwell has said in interviews that his portrayal of Zaphrod was influenced by three people: Bill Clinton, Elvis Presley and Vince Vaughn. Many viewers find resemblance to George W. Bush as well. Sam Rockwell would go in to portray George W. Bush in the 2018 film Vice.

In a chaotic scene shot in London, fans can spot Douglas Adams's brother James Thrift, sister Jane Garnier and daughter Polly Jane Rocket Adams rushing about in the general panic, as the earth is destroyed by the Vogons.

Both actors who play Marvin in the movie (Alan Rickman as his voice, Warwick Davis as his body) portray Hogwarts professors in the Harry Potter series. Rickman is Severus Snape, Davis is Filius Flitwick. Richard Griffiths, Who voices Prostetnic Vogon Jeltz in the film played Harry Potter's uncle Vernon Dursley in the Harry Potter movies.

The "babel fish" translator that Ford puts in Arthur's ear inspired the Babelfish web page (first on Altavista, now on Yahoo), which provides translations to and from different languages. The name "Babelfish," in turn, is named for the Tower of Babel in the Bible's Genesis.

Thomas Lennon was originally considered for the role of Ford Perfect before eventually being cast as the voice of Eddie the Computer.

One major change originally made for the film (and apparently the only one not originating from Douglas Adams) was that Trillian was to have been revealed as being only half-human. This plot point is referenced in pre-release publicity including the film-tie-in reissue of the original novel, cast and director interviews and the official "making of" book. Before release, however, this plot point was deleted from the film.

When hurriedly giving possible questions to what the answer 42 might mean, Arthur suggests "How many roads must a man walk down?", the first line of the Bob Dylan song "Blowin' In The Wind".

The hymn sung by the Jatravartidian followers of Humma Kavula was recorded at St. Martin's Church, Highgate, London on 19 June 2004. The hymn was sung by several hundred untrained members of the public invited to the recording via a call for singers circulated on the Internet.

Jack Davenport was considered for the role of Arthur Dent, but in the end it was decided he was simply too good-looking for the role of the ultimate everyman Dent. Douglas Adams had originally wanted Hugh Grant to also play Arthur, but the idea was nixed.

The pub which Ford takes Arthur to in the beginning is the Beehive Pub of Hertfordshire, England.

Douglas Adams once stated that the only character that absolutely had to be English was Arthur Dent. The fact that Ford was played by African American actor, Yasiin Bey, is not a significant deviation from the source material. Very few details are given about Ford's physical appearance in the book. Additionally, both Zaphod and Trillian (who is described as vaguely Arabic looking) are played by American actors Sam Rockwell and Zooey Deschanel.

Around 1990, a then-unknown Tim Roth was seriously considered to play Arthur Dent.

When the Vogons are preparing to destroy Earth, a large radio dish can be seen (surrounded by a sheep paddock). It is the Jodrell Bank Radio Telescope in Cheshire, England.

The note that Ford uses in the pub to buy six pints "and keep the change" is a £50 Bank of England note with the engraving of Sir John Houblon on the back. In the original 1978 radio version and in The Hitchhiker's Guide to the Galaxy (1981), it was "a fiver".

When Arthur and Slartibartfast move from the loading bay on their way to the factory floor, another carriage is seen entering the room and a klaxon sounds. This is the same klaxon that sounds at UK fairground rides (such as the ghost train) to signal the end/start of the ride.

The initial dolphin dance scene was filmed in the "Loro Parque" Zoo, in Puerto de la Cruz, Tenerife, Spain, the only place in Europe to feature an "Orca Ocean", and site of the world's largest parrot collection.

"Journey of the Sorcerer" is the song that plays when the book is first introduced (floating in space), It was originally performed by The Eagles, and used for as the theme music for the original radio series.

After Jay Roach decided to pass on directing the movie, he brought the property to Spike Jonze. Jonze also passed, but suggested Nick Goldsmith and Garth Jennings (also known as Hammer and Tongs, also soon-to-be former music video directors), who accepted.

The Magrathean holomessage appears as if it would become three dimensional with red/blue 3D glasses, but it is actually more of a Convergence calibration issue. It doesn't actually become 3D; he's only rimmed with red and blue, as he would if the convergence was aligned off-center. If it were a real 3D effect his whole face would be blurred with red/blue overlays.

Stephen Fry, who inherited the role of the Guide from the late Peter Jones, was a close friend of the late Douglas Adams. They were also both graduates of Cambridge University, although Fry was five years younger.

Despite the fact that this was filmed in Super 35, "Filmed in Panavision" is listed in the end credits.

The song "So Long and Thanks For All the Fish" was on the longlist for nominations for the Academy Award for Best Original Song, but was ultimately not nominated.

Arthur lives in Cottington.

The phone which Arthur uses in the first part of the film is a Nokia 7610.

Paula Nancy Millstone Jennings is based off real life poet Paul Neil Milne Johnstone. He asked Douglas Adams to alter the name for the Guide franchise. The original Johnstone name appears only in the radio show and in the 1979 printing of the novel. Jennings appears everywhere else including here.

In the fourth book of The Hitchhiker's Guide to the Galaxy book series, there is a character named John Watson, which is the name of Martin Freeman's character in Sherlock (2010) Another Sherlock Holmes connection, Stephen Fry (the narrator of the guide book) played Mycroft Holmes in the film sequel - Sherlock Holmes: A Game of Shadows (2011) starring Robert Downey Jr & Jude Law as Holmes & Watson, respectively.

When rescuing Trillian on Vogsphere, anytime someone has an idea or thinks, they get smacked in the face. Except the Leader of Vogshpere when he says "I think I'll have soup today".

Bill Nighy previously appeared as Sam in the BBC Radio drama of The Lord of the Rings. Also appearing in that production was Jack May, who appeared in the television series of Hitchhiker's Guide. Martin Freeman played a hobbit in The Hobbit: The Desolation of Smaug (2013), which also featured Stephen Fry.

Ix is the name of a planet in the Dune Universe.

This is the second science fiction comedy film that Alan Rickman and Sam Rockwell starred in since Galaxy Quest (1999).

There is/was a Hitchiker's Guide to the Galaxy appreciation society called ZZ9 plural Z Alpha. The had meetings, called "slouches", mainly in Slough, in pubs and often frequented by Douglas Adams.

The registration of Arthur's caravan is T863 XT0.

Oliver Postgate auditioned for the voice of the Book.

Martin Freeman later played a young Bilbo Baggins, a role previously played by Ian Holm. Holm appeared in his own film about space travel, Alien (1979).

Ford says that when he first arrived on Earth, he tried to shake hands with a car, thinking that automobiles were the dominant life form on Earth. Interestingly, the 2006 Pixar film Cars and its sequels take place in a world entirely populated by anthropomorphic vehicles.

Su Elliot: When Ford and Arthur drink at the pub early on, a middle-aged blonde can be seen watching them. According to the DVD commentary, this actress played Trillian in the London stage version of the story, a fact the director Garth Jennings was unaware of until the day of shooting.

Simon Jones: the original Arthur, handpicked by friend Douglas Adams for the radio show and TV's The Hitchhiker's Guide to the Galaxy (1981), makes a brief appearance as the Magrathean "greeting/threat" holomessage. This marks another slight deviation from the other Guide incarnations, as all other versions used Slartibartfast's likeness for the holomessage.

As the Heart of Gold Spaceship travels through "improbability" it quickly transforms into many strange shapes (including a rubber duck); in the very final transformation at the end, it quickly transforms into the face of author/creator Douglas Adams.