The Hitchhiker's Guide to the Galaxy

The first radio series of six episodes (called "Fits" after the names of the sections of Lewis Carroll's nonsense poem "The Hunting of the Snark")[15] was broadcast in 1978 on BBC Radio 4. Despite a low-key launch of the series (the first episode was broadcast at 10:30 pm on Wednesday, 8 March 1978), it received generally good reviews and a tremendous audience reaction for radio.[16] A one-off episode (a "Christmas special") was broadcast later in the year. The BBC had a practice at the time of commissioning "Christmas Special" episodes for popular radio series, and while an early draft of this episode of The Hitchhiker's Guide had a Christmas-related plotline, it was decided to be "in slightly poor taste" and the episode as transmitted served as a bridge between the two series.[17] This episode was released as part of the second radio series and, later, The Secondary Phase on cassettes and CDs. The Primary and Secondary Phases were aired, in a slightly edited version, in the United States on NPR Playhouse.

The first series was repeated twice in 1978 alone and many more times in the next few years. This led to an LP re-recording, produced independently of the BBC for sale, and a further adaptation of the series as a book. A second radio series, which consisted of a further five episodes, and bringing the total number of episodes to 12, was broadcast in 1980.

The radio series (and the LP and TV versions) were narrated by comedy actor Peter Jones as The Book. Jones was cast after a three-month-long casting search and after at least three actors (including Michael Palin) turning down the role.[18]

The series was also notable for its use of sound, being the first comedy series to be produced in stereo.[19] Adams said that he wanted the programme's production to be comparable to that of a modern rock album. Much of the programme's budget was spent on sound effects, which were largely the work of Paddy Kingsland (for the pilot episode and the complete second series) at the BBC Radiophonic Workshop and Dick Mills and Harry Parker (for the remaining episodes (2–6) of the first series). The fact that they were at the forefront of modern radio production in 1978 and 1980 was reflected when the three new series of Hitchhiker's became some of the first radio shows to be mixed into four-channel Dolby Surround. This mix was also featured on DVD releases of the third radio series.

The theme tune used for the radio, television, LP, and film versions is "Journey of the Sorcerer", an instrumental piece composed by Bernie Leadon and recorded by the Eagles on their 1975 album One of These Nights. Only the transmitted radio series used the original recording; a sound-alike cover by Tim Souster was used for the LP and TV series, another arrangement by Joby Talbot was used for the 2005 film, and still another arrangement, this time by Philip Pope, was recorded to be released with the CDs of the last three radio series. Apparently, Adams chose this song for its futuristic-sounding nature, but also for the fact that it had a banjo in it, which, as Geoffrey Perkins recalls, Adams said would give an "on the road, hitch-hiking feel" to it.[20]

The twelve episodes were released (in a slightly edited form, removing the Pink Floyd music and two other tunes "hummed" by Marvin when the team land on Magrathea) on CD and cassette in 1988, becoming the first CD release in the BBC Radio Collection. They were re-released in 1992, and at this time Adams suggested that they could retitle Fits the First to Sixth as "The Primary Phase" and Fits the Seventh to Twelfth as "The Secondary Phase" instead of just "the first series" and "the second series".[21] It was at about this time that a "Tertiary Phase" was first discussed with Dirk Maggs, adapting Life, the Universe and Everything, but this series would not be recorded for another ten years.[22]

On 21 June 2004, the BBC announced in a press release[23] that a new series of Hitchhiker's based on the third novel would be broadcast as part of its autumn schedule, produced by Above the Title Productions Ltd. The episodes were recorded in late 2003, but actual transmission was delayed while an agreement was reached with The Walt Disney Company over Internet re-broadcasts, as Disney had begun pre-production on the film.[24] This was followed by news that further series would be produced based on the fourth and fifth novels.

The third series was broadcast in September and October 2004. The fourth and fifth were broadcast in May and June 2005, with the fifth series following immediately after the fourth. CD releases accompanied the transmission of the final episode in each series.

The adaptation of the third novel followed the book very closely, which caused major structural issues in meshing with the preceding radio series in comparison to the second novel. Because many events from the radio series were omitted from the second novel, and those that did occur happened in a different order, the two series split in completely different directions. The last two adaptations vary somewhat—some events in Mostly Harmless are now foreshadowed in the adaptation of So Long and Thanks For All The Fish, while both include some additional material that builds on incidents in the third series to tie all five (and their divergent plotlines) together, most especially including the character Zaphod more prominently in the final chapters and addressing his altered reality to include the events of the Secondary Phase. While Mostly Harmless originally contained a rather bleak ending, Dirk Maggs created a different ending for the transmitted radio version, ending it on a much more upbeat note, reuniting the cast one last time.

The core cast for the third to fifth radio series remained the same, except for the replacement of Peter Jones by William Franklyn as the Book, and Richard Vernon by Richard Griffiths as Slartibartfast, since both had died. (Homage to Jones' iconic portrayal of the Book was paid twice: the gradual shift of voices to a "new" version in episode 13, launching the new productions, and a blend of Jones and Franklyn's voices at the end of the final episode, the first part of Maggs' alternative ending.) Sandra Dickinson, who played Trillian in the TV series, here played Tricia McMillan, an English-born, American-accented alternate-universe version of Trillian, while David Dixon, the television series' Ford Prefect, made a cameo appearance as the "Ecological Man". Jane Horrocks appeared in the new semi-regular role of Fenchurch, Arthur's girlfriend, and Samantha Béart joined in the final series as Arthur and Trillian's daughter, Random Dent. Also reprising their roles from the original radio series were Jonathan Pryce as Zarniwoop (here blended with a character from the final novel to become Zarniwoop Vann Harl), Rula Lenska as Lintilla and her clones (and also as the Voice of the Bird), and Roy Hudd as Milliways compere Max Quordlepleen, as well as the original radio series' announcer, John Marsh.

The series also featured guest appearances by such noted personalities as Joanna Lumley as the Sydney Opera House Woman, Jackie Mason as the East River Creature, Miriam Margolyes as the Smelly Photocopier Woman, BBC Radio cricket legends Henry Blofeld and Fred Trueman as themselves, June Whitfield as the Raffle Woman, Leslie Phillips as Hactar, Saeed Jaffrey as the Man on the Pole, Sir Patrick Moore as himself, and Christian Slater as Wonko the Sane. Finally, Adams himself played the role of Agrajag, a performance adapted from his book-on-tape reading of the third novel, and edited into the series created some time after the author's death.

The first of six episodes in a sixth series, the Hexagonal Phase, was broadcast on BBC Radio 4 on 8 March 2018[25] and featured Professor Stephen Hawking introducing himself as the voice of The Hitchhiker's Guide to the Galaxy Mk II by saying: "I have been quite popular in my time. Some even read my books."

The first book was adapted from the first four radio episodes (the Primary Phase), with Arthur being rescued from Earth's destruction by Ford, meeting Zaphod and Trillian, coming to the planet of Magrathea and discovering the true purpose of Earth, and ending with the group preparing to go to the Restaurant at the End of the Universe. It was first published in 1979, initially in paperback, by Pan Books, after BBC Publishing had turned down the offer of publishing a novelisation, an action they would later regret.[27] The book reached number one on the book charts in only its second week, and sold over 250,000 copies within three months of its release. A hardback edition was published by Harmony Books, a division of Random House in the United States in October 1980, and the 1981 US paperback edition was promoted by the give-away of 3,000 free copies in the magazine Rolling Stone to build word of mouth. In 2005, Del Rey Books re-released the Hitchhiker series with new covers for the release of the 2005 movie. To date, it has sold over 14 million copies.[28]

A photo-illustrated edition of the first novel appeared in 1994.

In The Restaurant at the End of the Universe (published in 1980), Zaphod is separated from the others and finds he is part of a conspiracy to uncover who really runs the Universe. Zaphod meets Zarniwoop, a conspirator and editor for The Guide, who knows where to find the secret ruler. Zaphod becomes briefly reunited with the others for a trip to Milliways, the restaurant of the title. Zaphod and Ford decide to steal a ship from there, which turns out to be a stunt ship pre-programmed to plunge into a star as a special effect in a stage show. Unable to change course, the main characters get Marvin to run the teleporter they find in the ship, which is working other than having no automatic control (someone must remain behind to operate it), and Marvin seemingly sacrifices himself. Zaphod and Trillian discover that the Universe is in the safe hands of a simple man living on a remote planet in a wooden shack with his cat.

Ford and Arthur, meanwhile, end up on a spacecraft full of the outcasts of the Golgafrinchan civilisation. The ship crashes on prehistoric Earth; Ford and Arthur are stranded, and it becomes clear that the inept Golgafrinchans are the ancestors of modern humans, having displaced the Earth's indigenous hominids. This has disrupted the Earth's programming so that when Ford and Arthur manage to extract the final readout from Arthur's subconscious mind by pulling lettered tiles from a Scrabble set, it is "What do you get if you multiply six by nine?" Arthur then comments, "I've always said there was something fundamentally wrong with the universe."

The book was adapted from the remaining material in the radio series—covering from the fifth episode to the twelfth episode, although the ordering was greatly changed (in particular, the events of Fit the Sixth, with Ford and Arthur being stranded on pre-historic Earth, end the book, and their rescue in Fit the Seventh is deleted), and most of the Brontitall incident was omitted, instead of the Haggunenon sequence, co-written by John Loyd, the Disaster Area stunt ship was substituted—this having first been introduced in the LP version. Adams himself considered Restaurant to be his best novel of the five.[29]

In Life, the Universe and Everything (published in 1982), Ford and Arthur travel through the space-time continuum from prehistoric Earth to Lord's Cricket Ground. There they run into Slartibartfast, who enlists their aid in preventing galactic war. Long ago, the people of Krikkit attempted to wipe out all life in the Universe, but they were stopped and imprisoned on their home planet; now they are poised to escape. With the help of Marvin, Zaphod, and Trillian, our heroes prevent the destruction of life in the Universe and go their separate ways.

This was the first Hitchhiker's book originally written as a book and not adapted from radio. Its story was based on a treatment Adams had written for a Doctor Who theatrical release,[30] with the Doctor role being split between Slartibartfast (to begin with), and later Trillian and Arthur.

The front cover of The Ultimate Hitchhiker's Guide, a collection of the five books in the series written before Adams's death, a leatherbound volume published in the United States by Portland House, a division of Random House, in 1997

In 2004, it was adapted for radio as the Tertiary Phase of the radio series.

In So Long, and Thanks for All the Fish (published in 1984), Arthur returns home to Earth, rather surprisingly since it was destroyed when he left. He meets and falls in love with a girl named Fenchurch, and discovers this Earth is a replacement provided by the dolphins in their Save the Humans campaign. Eventually, he rejoins Ford, who claims to have saved the Universe in the meantime, to hitch-hike one last time and see God's Final Message to His Creation. Along the way, they are joined by Marvin, the Paranoid Android, who, although 37 times older than the universe itself (what with time travel and all), has just enough power left in his failing body to read the message and feel better about it all before expiring.

This was the first Hitchhiker's novel which was not an adaptation of any previously written story or script. In 2005 it was adapted for radio as the Quandary Phase of the radio series.

Finally, in Mostly Harmless (published in 1992), Vogons take over The Hitchhiker's Guide (under the name of InfiniDim Enterprises), to finish, once and for all, the task of obliterating the Earth. After abruptly losing Fenchurch and travelling around the galaxy despondently, Arthur's spaceship crashes on the planet Lamuella, where he settles in happily as the official sandwich-maker for a small village of simple, peaceful people. Meanwhile, Ford Prefect breaks into The Guide's offices, gets himself an infinite expense account from the computer system, and then meets The Hitchhiker's Guide to the Galaxy, Mark II, an artificially intelligent, multi-dimensional guide with vast power and a hidden purpose. After he declines this dangerously powerful machine's aid (which he receives anyway), he sends it to Arthur Dent for safety ("Oh yes, whose?"—Arthur).

Trillian uses DNA that Arthur donated for travelling money to have a daughter, and when she goes to cover a war, she leaves her daughter Random Frequent Flyer Dent with Arthur. Random, a more than typically troubled teenager, steals The Guide Mark II and uses it to get to Earth. Arthur, Ford, Trillian, and Tricia McMillan (Trillian in this alternate universe) follow her to a crowded club, where an anguished Random becomes startled by a noise and inadvertently fires her gun at Arthur. The shot misses Arthur and kills a man (the ever-unfortunate Agrajag). Immediately afterwards, The Guide Mark II causes the removal of all possible Earths from probability. All of the main characters, save Zaphod, were on Earth at the time and are apparently killed, bringing a good deal of satisfaction to the Vogons.

In 2005 it was adapted for radio as the Quintessential Phase of the radio series, with the final episode first transmitted on 21 June 2005.

It was announced in September 2008 that Eoin Colfer, author of Artemis Fowl, had been commissioned to write the sixth instalment entitled And Another Thing... with the support of Jane Belson, Adams's widow.[31][32] The book was published by Penguin Books in the UK and Hyperion in the US in October 2009.[31][33]

The story begins as death rays bear down on Earth, and the characters awaken from a virtual reality. Zaphod picks them up shortly before they are killed, but completely fails to escape the death beams. They are then saved by Bowerick Wowbagger, the Infinitely Prolonged, whom they agree to help kill. Zaphod travels to Asgard to get Thor's help. In the meantime, the Vogons are heading to destroy a colony of people who also escaped Earth's destruction, on the planet Nano. Arthur, Wowbagger, Trillian and Random head to Nano to try to stop the Vogons, and on the journey, Wowbagger and Trillian fall in love, making Wowbagger question whether or not he wants to be killed. Zaphod arrives with Thor, who then signs up to be the planet's God. With Random's help, Thor almost kills Wowbagger. Wowbagger, who merely loses his immortality, then marries Trillian.

Thor then stops the first Vogon attack and apparently dies. Meanwhile, Constant Mown, son of Prostetnic Jeltz, convinces his father that the people on the planet are not citizens of Earth, but are, in fact, citizens of Nano, which means that it would be illegal to kill them. As the book draws to a close, Arthur is on his way to check out a possible university for Random, when, during a hyperspace jump, he is flung across alternate universes, has a brief encounter with Fenchurch, and ends up exactly where he would want to be. And then the Vogons turn up again.

In 2017 it was adapted for radio as the Hexagonal Phase of the radio series, with its premiere episode first transmitted on 8 March 2018[34][35] (exactly forty years, to the day, from the first episode of the first series, the Primary Phase[36]).

Two omnibus editions were created by Douglas Adams to combine the Hitchhiker series novels and to "set the record straight".[37] The stories came in so many different formats that Adams stated that every time he told it he would contradict himself. Therefore, he stated in the introduction of The More Than Complete Hitchhiker's Guide that "anything I put down wrong here is, as far as I'm concerned, wrong for good."[37] The two omnibus editions were The More Than Complete Hitchhiker's Guide, Complete and Unabridged (published in 1987) and The Ultimate Hitchhiker's Guide, Complete and Unabridged (published in 1997).

Published in 1987, this 624-page leatherbound omnibus edition contains "wrong for good"[37] versions of the four Hitchhiker series novels at the time, and also includes one short story:

• The Hitchhiker's Guide to the Galaxy
• The Restaurant at the End of the Universe
• Life, the Universe and Everything
• So Long, and Thanks for All the Fish
• "Young Zaphod Plays it Safe"

Published in 1997, this 832-page leatherbound final omnibus edition contains five Hitchhiker series novels and one short story:

• The Hitchhiker's Guide to the Galaxy
• The Restaurant at the End of the Universe
• Life, the Universe and Everything
• So Long, and Thanks for All the Fish
• Mostly Harmless
• "Young Zaphod Plays it Safe"

Also appearing in The Ultimate Hitchhiker's Guide, at the end of Adams's introduction, is a list of instructions on "How to Leave the Planet", providing a humorous explanation of how one might replicate Arthur and Ford's feat at the beginning of Hitchhiker's.

The popularity of the radio series gave rise to a six-episode television series, directed and produced by Alan J. W. Bell, which first aired on BBC 2 in January and February 1981. It employed many of the actors from the radio series and was based mainly on the radio versions of Fits the First to Sixth. A second series was at one point planned, with a storyline, according to Alan Bell and Mark Wing-Davey that would have come from Adams's abandoned Doctor Who and the Krikkitmen project (instead of simply making a TV version of the second radio series). However, Adams got into disputes with the BBC (accounts differ: problems with budget, scripts, and having Alan Bell involved are all offered as causes), and the second series was never made. Elements of Doctor Who and the Krikkitmen were instead used in the third novel, Life, the Universe and Everything.

The main cast was the same as the original radio series, except for David Dixon as Ford Prefect instead of McGivern, and Sandra Dickinson as Trillian instead of Sheridan.  [38]

A new television series for Hulu was announced in July 2019. Carlton Cuse was named as the showrunner alongside Jason Fuchs, who will also be writing for the show. The show will be produced by ABC Signature and Genre Arts.[39] The series was set to premiere in 2021. Production was slated to begin in the summer of 2020 and air on Fox in international markets.[40] The series has reportedly been renewed for a second season. Due to the COVID-19 pandemic, production on the series has most likely been delayed.[41] However, a production outlet claimed that the series began production in May 2021.[42][43]

Segments of several of the books were adapted as part of the BBC's The Big Read survey and programme, broadcast in late 2003. The film, directed by Deep Sehgal, starred Sanjeev Bhaskar as Arthur Dent, alongside Spencer Brown as Ford Prefect, Nigel Planer as the voice of Marvin, Stephen Hawking as the voice of Deep Thought, Patrick Moore as the voice of the Guide, Roger Lloyd-Pack as Slartibartfast, and Adam Buxton and Joe Cornish as Loonquawl and Phouchg.

The first four radio episodes were adapted for a double LP, also entitled The Hitchhiker's Guide to the Galaxy (appended with "Part One" for the subsequent Canadian release), first by mail-order only, and later into stores. The double LP and its sequel were originally released by Original Records in the United Kingdom in 1979 and 1980, with the catalogue numbers ORA042 and ORA054 respectively. They were first released by Hannibal Records in 1982 (as HNBL 2301 and HNBL 1307, respectively) in the United States and Canada, and later re-released in a slightly abridged edition by Simon & Schuster's Audioworks in the mid-1980s. Both were produced by Geoffrey Perkins and featured cover artwork by Hipgnosis.

The script in the first double LP very closely follows the first four radio episodes, although further cuts had to be made for reasons of timing. Despite this, other lines of dialogue that were indicated as having been cut when the original scripts from the radio series were eventually published can be heard in the LP version. The Simon & Schuster cassettes omit the Veet Voojagig narration, the cheerleader's speech as Deep Thought concludes its seven-and-one-half-million-year programme, and a few other lines from both sides of the second LP of the set.

Most of the original cast returned, except for Susan Sheridan, who was recording a voice for the character of Princess Eilonwy in The Black Cauldron for Walt Disney Pictures. Cindy Oswin voiced Trillian on all three LPs in her place. Other casting changes in the first double LP included Stephen Moore taking on the additional role of the barman, and Valentine Dyall as the voice of Deep Thought. Adams's voice can be heard making the public address announcements on Magrathea.

Because of copyright issues, the music used during the first radio series was either replaced, or in the case of the title it was re-recorded in a new arrangement. Composer Tim Souster did both duties (with Paddy Kingsland contributing music as well), and Souster's version of the theme was the version also used for the eventual television series.[61]

The sequel LP was released, singly, as The Hitchhiker's Guide to the Galaxy Part Two: The Restaurant at the End of the Universe in the UK, and simply as The Restaurant at the End of the Universe in the USA. The script here mostly follows Fit the Fifth and Fit the Sixth, but includes a song by the backup band in the restaurant ("Reg Nullify and his Cataclysmic Combo"), and changes the Haggunenon sequence to "Disaster Area".

As the result of a misunderstanding, the second record was released before being cut down in a final edit that Douglas Adams and Geoffrey Perkins had both intended to make. Perkins has said, "[I]t is far too long on each side. It's just a rough cut. [...] I felt it was flabby, and I wanted to speed it up."[62] The Simon & Schuster Audioworks re-release of this LP was also abridged slightly from its original release. The scene with Ford Prefect and Hotblack Desiato's bodyguard is omitted.

Sales for the first double-LP release were primarily through mail order. Total sales reached over 60,000 units, with half of those being mail order, and the other half through retail outlets.[63] This is in spite of the facts that Original Records' warehouse ordered and stocked more copies than they were actually selling for quite some time, and that Paul Neil Milne Johnstone complained about his name and then-current address being included in the recording.[64] This was corrected for a later pressing of the double-LP by "cut[ting] up that part of the master tape and reassembl[ing] it in the wrong order".[65] The second LP release ("Part Two") also only sold a total of 60,000 units in the UK.[63] The distribution deals for the United States and Canada with Hannibal Records and Simon and Schuster were later negotiated by Douglas Adams and his agent, Ed Victor, after gaining full rights to the recordings from Original Records, which went bankrupt.[66]

All five phases were released on LP in 2018 by Demon Records, and for its 42nd anniversary, the original Hitchhiker's Guide and Restaurant at the End of the Universe were combined into a three-record set that was released in August 2020 for Record Store Day, also by Demon Records. It is available in three versions: Translucent Vogon Green, Translucent Magrathean Blue and Translucent Pan-Galactic Purple.

There have been three audiobook recordings of the novel. The first was an abridged edition (ISBN 0-671-62964-6), recorded in the mid-1980s for the EMI label Music For Pleasure by Stephen Moore, best known for playing the voice of Marvin the Paranoid Android in the radio series and in the TV series. In 1990, Adams himself recorded an unabridged edition for Dove Audiobooks (ISBN 1-55800-273-1), later re-released by New Millennium Audio (ISBN 1-59007-257-X) in the United States and available from BBC Audiobooks in the United Kingdom. Also by arrangement with Dove, ISIS Publishing Ltd produced a numbered exclusive edition signed by Douglas Adams (ISBN 1-85695-028-X) in 1994. To tie-in with the 2005 film, actor Stephen Fry, the film's voice of the Guide, recorded a second abridged edition (ISBN 0-7393-2220-6).

In addition, unabridged versions of books 2-5 of the series were recorded by Martin Freeman for Random House Audio. Freeman plays Arthur in the 2005 film adaptation. Audiobooks 2-5 follow in order and include: The Restaurant at the End of the Universe (ISBN 9780739332085); Life, the Universe, and Everything (ISBN 9780739332108); So Long, and Thanks for All the Fish (ISBN 9780739332122); and Mostly Harmless (ISBN 9780739332146).

Sometime between 1982 and 1984 (accounts differ), the British company Supersoft published a text-based adventure game based on the book, which was released in versions for the Commodore PET and Commodore 64. One account states that there was a dispute as to whether valid permission for publication had been granted, and following legal action the game was withdrawn and all remaining copies were destroyed. Another account states that the programmer, Bob Chappell, rewrote the game to remove all Hitchhiker's references, and republished it as "Cosmic Capers".[67]

Officially, the TV series was followed in 1984 by a best-selling "interactive fiction", or text-based adventure game, distributed by Infocom. It was designed by Adams and Infocom regular Steve Meretzky[68] and was one of Infocom's most successful games.[69] As with many Infocom games, the box contained a number of "feelies" including a "Don't panic" badge, some "pocket fluff", a pair of peril-sensitive sunglasses (made of cardboard), an order for the destruction of the Earth, a small, clear plastic bag containing "a microscopic battle fleet" and an order for the destruction of Arthur Dent's house (signed by Adams and Meretzky).[70]

In September 2004, it was revived by the BBC on the Hitchhiker's section of the Radio 4 website for the initial broadcast of the Tertiary Phase, and is still available to play online.[71][72] This new version uses an original Infocom datafile with a custom-written interpreter, by Sean Sollé, and Flash programming by Shimon Young, both of whom used to work at The Digital Village (TDV). The new version includes illustrations by Rod Lord, who was head of Pearce Animation Studios in 1980, which produced the guide graphics for the TV series. On 2 March 2005 it won the Interactive BAFTA in the "best online entertainment" category.[73][74]

A sequel to the original Infocom game was never made. An all-new, fully graphical game was designed and developed by a joint venture between The Digital Village and PAN Interactive (no connection to Pan Books / Pan MacMillan).[75][76] This new game was planned and developed between 1998 and 2002, but like the sequel to the Infocom game, it also never materialised.[77] In April 2005, Starwave Mobile released two mobile games to accompany the release of the film adaptation. The first, developed by Atatio, was called The Hitchhiker's Guide to the Galaxy: Vogon Planet Destructor.[78] It was a typical top-down shooter and except for the title had little to do with the actual story. The second game, developed by TKO Software, was a graphical adventure game named The Hitchhiker's Guide to the Galaxy: Adventure Game.[79] Despite its name, the newly designed puzzles by TKO Software's Ireland studio were different from the Infocom ones, and the game followed the movie's script closely and included the new characters and places. The Adventure Game won the IGN's "Editors' Choice Award" in May 2005.

On 25 May 2011, Hothead Games announced they were working on a new edition of The Guide.[80] Along with the announcement, Hothead Games launched a teaser web site made to look like an announcement from Megadodo Publications that The Guide will soon be available on Earth.[81] It has since been revealed that they are developing an iOS app in the style of the fictional Guide.[82]

The front cover of the DC Comics adaptation of the first book

In 1993, DC Comics, in conjunction with Byron Preiss Visual Publications, published a three-part comic book adaptation of the novelisation of The Hitchhiker's Guide to the Galaxy. This was followed up with three-part adaptations of The Restaurant at the End of the Universe in 1994, and Life, the Universe and Everything in 1996. There was also a series of collectors' cards with art from and inspired by the comic adaptations of the first book, and a graphic novelisation (or "collected edition") combining the three individual comic books from 1993, itself released in May 1997. Douglas Adams was deeply opposed to the use of American English spellings and idioms in what he felt was a very British story, and had to be talked into it by the American publishers, although he remained very unhappy with the compromise.

The adaptations were scripted by John Carnell. Steve Leialoha provided the art for Hitchhiker's and the layouts for Restaurant. Shepherd Hendrix did the finished art for Restaurant. Neil Vokes and John Nyberg did the finished artwork for Life, based on breakdowns by Paris Cullins (Book 1) and Christopher Schenck (Books 2–3). The miniseries were edited by Howard Zimmerman and Ken Grobe.

On Saturday 29 March 2014, Radio 4 broadcast an adaptation in front of a live audience, featuring many members of the original cast including Stephen Moore, Susan Sheridan, Mark Wing-Davey, Simon Jones and Geoff McGivern, with John Lloyd as the book.[83]

The adaptation was adapted by Dirk Maggs primarily from Fit the First, including material from the books and later radio Fits as well as some new jokes. It formed part of Radio 4's Character Invasion series.[84]

While Adams' writing in The Hitchhiker's Guide was mostly to poke fun at scientific advance, such as through the artificial personalities built into the work's robots, Adams had predicted some concepts that have since come to be reality. The Guide itself, described as a small book-sized object that held a great volume of information, predated computer laptops and is comparable to tablet computers. The idea of being able to instantaneously translate between any language, a function provided by the Babel Fish, has since become possible with several software products that work in near real-time.[85] In the Hitchhiker's Guide to the Galaxy, Adams also mentions computers being controlled by voice, touch and gesture, a reality for humans today.

Towel day Innsbruck- Towels with a silkscreen print as homage to Douglas Adams. Next to the words 'DON'T PANIC' there are the GPS data from the city Innsbruck where Adams had the idea for the 'Hitchhiker's Guide To The Galaxy [86].

Many merchandising and spin-off items (or "Hitch-Hikeriana") were produced in the early 1980s, including towels in different colours, all bearing the Guide entry for towels. Later runs of towels include those made for promotions by Pan Books, Touchstone Pictures / Disney for the 2005 movie, and different towels made for ZZ9 Plural Z Alpha, the official Hitchhiker's Appreciation society.[87] Other items that first appeared in the mid-1980s were T-shirts, including those made for Infocom (such as one bearing the legend "I got the Babel Fish" for successfully completing one of that game's most difficult puzzles), and a Disaster Area tour T-shirt. Other official items have included "Beeblebears" (teddy bears with an extra head and arm, named after Hitchhiker's character Zaphod Beeblebrox, sold by the official Appreciation Society), an assortment of pin-on buttons and a number of novelty singles. Many of the above items are displayed throughout the 2004 "25th Anniversary Illustrated Edition" of the novel, which used items from the personal collections of fans of the series.

Stephen Moore recorded two novelty singles in character as Marvin, the Paranoid Android: "Marvin"/"Metal Man" and "Reasons To Be Miserable"/"Marvin I Love You". The last song has appeared on a Dr. Demento compilation. Another single featured the re-recorded "Journey of the Sorcerer" (arranged by Tim Souster) backed with "Reg Nullify In Concert" by Reg Nullify, and "Only the End of the World Again" by Disaster Area (including Douglas Adams on bass guitar) listen^ⓘ. These discs have since become collector's items.

The 2005 movie also added quite a few collectibles, mostly through the National Entertainment Collectibles Association. These included three prop replicas of objects seen on the Vogon ship and homeworld (a mug, a pen and a stapler), sets of "action figures" with a height of either 3 or 6 inches (76 or 150 mm), a gun—based on a prop used by Marvin, the Paranoid Android, that shoots foam darts—a crystal cube, shot glasses, a ten-inch (254 mm) high version of Marvin with eyes that light up green, and "yarn doll" versions of Arthur Dent, Ford Prefect, Trillian, Marvin and Zaphod Beeblebrox. Also, various audio tracks were released to coincide with the movie, notably re-recordings of "Marvin" and "Reasons To Be Miserable", sung by Stephen Fry, along with some of the "Guide Entries", newly written material read in-character by Fry.

Celebrated on 25 May, Towel Day is a fan-created event in which they carry a towel with them throughout the day, in reference to the importance of towels as a tool of a galactic hitchhiker described in the work. The annual event was started in 2001 two weeks after Adams' death.[88]

In the works, the number 42 is given as The Answer to the Ultimate Question of Life, The Universe, and Everything by the computer Deep Thought. The absurdly simple answer to a complex philosophical question became a frequent reference in popular culture in homage to The Hitchhiker's Guide, particularly within works of science fiction and in video games, such as in Doctor Who, Lost, Star Trek and The X-Files.[89][90]

2020 was the 42nd anniversary of HG2G appearing on Radio 4. The book Hitchhiking: Cultural Inroads was dedicated to the memory of British actor Stephen V. Moore who died in Oct 2019 and played the voice of Marvin the Paranoid Android in the original BBC Radio and Television Series.[91]

"Don't Panic" appears on the dashboard of the space-bound Tesla Roadster launched by SpaceX.

Two asteroids, 18610 Arthurdent[92] and 25924 Douglasadams[93] were named after Arthur Dent and Douglas Adams, as both had been discovered shortly after Adams' death in 2001. The fish species Bidenichthys beeblebroxi and moth species Erechthias beeblebroxi were both named after the character of Zaphod Beeblebrox.[90]

Radiohead's song "Paranoid Android" was named after the character of Marvin the Paranoid Android. The band's singer Thom Yorke used the character's name jokingly, as the song was not about depression, but Yorke knew many of his fans felt that he should seem to be depressed.[94] The album OK Computer which "Paranoid Android" appears on is also taken from The Hitchhiker's Guide, referencing how Zaphod would address the Heart of Gold's onboard computer Eddie, and was selected by the band after listening to the radio plays while travelling on tour.[95]

SpaceX CEO Elon Musk has stated that The Hitchhiker's Guide is one of his favourite works, his "favorite philosopher is Douglas Adams" and his favourite spaceship ever is in The Hitchhiker's Guide.[96] Musk said the attitude that Adams presented through The Hitchhiker's Guide had influenced the vision behind both SpaceX and Tesla Motors.[97] When Musk launched his Tesla Roadster into an elliptical heliocentric orbit as part of the initial test launch of the Falcon Heavy, he had a copy of Douglas Adams' novel The Hitchhiker's Guide to the Galaxy in the glovebox, along with references to the book in the form of a towel and a sign on the dashboard that reads "DON'T PANIC!", as a nod to the Hitchhiker's Guide.[98]

References to the series can be seen on websites, within TV and radio programmes, songs, and in console and computer games. Examples include borrowing Adams's characters' names, or references to the number 42, or other catchphrases, or even reusing "The Hitchhiker's Guide to ..." to title other books and articles (which Adams himself had borrowed from Ken Welsh's Hitch-hiker's Guide to Europe). Hitchhiker's references have also appeared in several series and episodes of another famous British science fiction series with which Adams was once affiliated: Doctor Who.

• The online Babel Fish translation service was also named in honour of a fictional creature that Adams created for the Hitchhiker's series.
• The 1980s British Pop band Level 42 attribute their name to the ultimate answer.
• The instant message program Trillian is also named after a lead Hitchhiker's character.
• The massive online game RuneScape has a small area named "Mos Le'Harmless" (which sounds like Mostly Harmless). Mostly Harmless was the body of the initially published, severely edited version of Ford's expanded entry for Earth (also used as the title of the fifth book).
• Internet search engines Google and MSN offer "42" as the answer to the search criteria "What is the answer to life the universe and everything?"
• In the Foster's Home for Imaginary Friends episode "Bus the Two of Us", Bloo picks up a hitchhiker holding a sign reading "Magrathea".
• In Adventure Quest, there is a door that says 42 on it. If clicked on it will say "This room contains the answers to the universe. It is locked, bolted, and duct taped shut", or "A tiny sign on the door reads 'Beware of LepardZard'".
• In the comic strip Get Fuzzy, Rob frequently wears a 6 times 9 = 42 shirt, and a strip paid tribute to Douglas Adams soon after his death.
• Coldplay named a song "Don't Panic": "the opening track to Parachutes and is a guitar-based song. It was originally called 'Panic' and was one of six songs played at Coldplay's first concert in 1998. Eventually, the title became 'Don't Panic', taken from Douglas Adams's The Hitchhiker's Guide to the Galaxy." Also on their album Viva La Vida there is a song called "42".
• The video game Fallout, the pre-rendered scenery in one location features a dead whale and a broken flowerpot, parodying a scene from the first book.
• In the video game Spore, at the centre of the universe the player may receive a Genesis Device known as the "Staff of Life". The device has 42 charges as well as an icon which reads "42".
• The rock band Perpetual Groove has an album entitled All This Everything in which many of the tracks are related to The Hitchhiker's Guide to the Galaxy. The first track is entitled "Life", the eighth "The Universe", and the last "And Everything". Other Hitchhiker's-related titles include "53 More Things to Do in Zero Gravity" and "Andromeda".
• The tabletop role-playing game GURPS says in one source book that a towel is one of the most important things an adventurer can have.

A short story by Adams, "Young Zaphod Plays It Safe", first appeared in 1986, in The Utterly Utterly Merry Comic Relief Christmas Book, a special large-print compilation of different stories and pictures that raised money for the then-new Comic Relief charity in the UK. The story also appears in some of the omnibus editions of the trilogy, and in The Salmon of Doubt. There are two versions of this story, one of which is slightly more explicit in its political commentary.

A novel, Douglas Adams' Starship Titanic: A Novel, written by Terry Jones, is based on Adams's computer game of the same name, Douglas Adams's Starship Titanic, which in turn is based on an idea from Life, the Universe and Everything. The idea concerns a luxury passenger starship that suffers "sudden and gratuitous total existence failure" on its maiden voyage.

Wowbagger the Infinitely Prolonged, a character from Life, the Universe and Everything, also appears in a short story by Adams titled "The Private Life of Genghis Khan" which appears in some early editions of The Salmon of Doubt.

Douglas Adams and Geoffrey Perkins collaborated on The Hitchhiker's Guide to the Galaxy: The Original Radio Scripts, first published in the United Kingdom and United States in 1985. A tenth-anniversary (of the script book publication) edition was printed in 1995, and a twenty-fifth-anniversary (of the first radio series broadcast) edition was printed in 2003.

The 2004 series was produced by Above The Title Productions and the scripts were published in July 2005, with production notes for each episode. This second radio script book is entitled The Hitchhiker's Guide to the Galaxy Radio Scripts: The Tertiary, Quandary and Quintessential Phases. Douglas Adams gets the primary writer's credit (as he wrote the original novels), and there is a foreword by Simon Jones, introductions by the producer and the director, and other introductory notes from other members of the cast.