!![[Franchise/TheHitchhikersGuideToTheGalaxy General franchise]] trivia:
* AdaptationSequence: Radio Serial > Books > TV Series > Adventure Game > Movie
* BeamMeUpScotty: Say it with me, people. It's "The Answer to the Ultimate Question of Life, the Universe and Everything". Not the meaning of life.
* LifeImitatesArt: Smartphones and tablets with access to Wikipedia mimic the capability and functions of the Guide with uncanny accuracy.
* RecycledScript:
** ''Literature/LifeTheUniverseAndEverything'' was based on an unused ''Series/DoctorWho'' script, ''Doctor Who and the Krikketmen''. It might have been a second Hitchhiker TV series.
** The later radio series were essentially adaptations of Adams' last three Hitchhiker novels, retconning pretty much the entire events of the second series to being merely the delusional rantings of Zaphod Beeblebrox, instead of following directly from them.
* TechnologyMarchesOn: Digital watches sure are a neat idea, huh? (In the later radio series, and the movie, they were replaced by mobile phones.)
* TropeNamer:
** BitsOfMeKeepPassingOut
** DeconstructorFleet (pun on Vogon Constructor Fleet)
** FutureImperfect
** GargleBlaster
** InsignificantLittleBluePlanet
** LetsMeetTheMeat
** PuffOfLogic
** RealityIsOutToLunch
** SoLongAndThanksForAllTheGear
* UnfortunateName: Slartibartfast. Adams wanted him to have an immense sadness, so gave him a terrible name. He started with [=FartyFuckBalls=], and mutated it until it sounded rude without actually being rude.

!![[Literature/TheHitchhikersGuideToTheGalaxy Novels]] trivia:
* AuthorExistenceFailure: TropeNamer, almost; the third book mentions a "total existence failure". Later, of course, succumbed to the trope when Adams died while working on the sixth book; his last published collection of pieces, ''The Salmon of Doubt'', contains an early draft of a ''Literature/DirkGently'' novel that Adams was hoping to rework into a Hitchhiker book.
* CreatorBreakdown: Regarding the DownerEnding of ''Mostly Harmless'' and the mixed-to-negative reaction from fans, Adams conceded, "I just had a thoroughly miserable year, and I was trying to write a book against that background." He intended a sixth book to give the series a better conclusion, but succumbed to AuthorExistenceFailure first.
* ExecutiveMeddling: In ''Life, the Universe, and Everything'', the Silver Bail of Peace is the Rory Award for "Most Gratuitous Use of the Word 'Fuck' in a Serious Screenplay". US censors were offended, and Adams, bowing to their wishes, promptly changed the offending word to "Belgium". Fortunately, [[RuleOfFunny the resulting passage was much funnier]], as Adams modified the surrounding conversation to fit the change, as well.
--> '''Arthur''': "Have you ever been to Belgium in fact?"


!![[Film/TheHitchhikersGuideToTheGalaxy Movie]] trivia:
* GodCreatedCanonForeigner: Many of the differences from previous versions were Adams creations, from pre-death versions of the script, including the POV Ray, the flyswatters, Humma Kavula, and the romantic elements.
* HeyItsThatGuy:
** Marvin is played by two Harry Potter alumni: Creator/WarwickDavis (that film franchise's Flitwick and many short characters) wears the suit, while Creator/AlanRickman (Snape's actor) supplies the voice.
** The newscaster is [[Series/BoardwalkEmpire Margaret Shroeder]].
** The TV version's Arthur Dent as the recorded message from Magrathea.
* HeyItsThatVoice:
** Marvin has the voice of Creator/AlanRickman.
** The Guide is voiced by Creator/StephenFry.
** Deep Thought is voiced by Creator/HelenMirren.
** Music/BillBailey as The Whale.
** Creator/RichardGriffiths is Jeltz, [[Recap/DoctorWhoS31E3VictoryOfTheDaleks Winston Churchill]] is Kwaltz, and the rest of the Vogons are Series/TheLeagueOfGentlemen!
* InMemoriam: "For Douglas."
* RetroactiveRecognition: The four leads are Creator/MartinFreeman, [[Film/BeKindRewind Mos Def]], Creator/ZooeyDeschanel, and Creator/SamRockwell. We later see Creator/JohnMalkovich and Creator/BillNighy.

!![[Radio/TheHitchhikersGuideToTheGalaxy Radio]] trivia:
* Slartibartfast is not named for the majority of the episode he first appears in. WordOfGod explained that it was a joke at the expense of the woman who had to type the scripts - that she'd typed this name a dozen times and he simply said 'My name is not important'.
* The seventh episode was originally broadcast on 24 December 1978. Consideration was given, partly due to the date and partly due to the fact that all the plot threads had been tied off at the end of episode six, to making it a stand-alone Christmas special in which Marvin would have been both figuratively and literally the star (of Bethlehem), and by participating in a nativity scene would be cured of his depression. In the end they made it a normal episode, devoted to untying enough plot threads for the series to continue.
* HeyItsThatVoice:
** In the original radio series, Creator/DavidJason was the Golgafrincham "B" Ark Captain, and Jim Broadbent played one of the complaining philosophers and one of the gun-happy cops on Magrathea.
** In the recent radio adaptations we have Creator/ChristianSlater as Wonko the Sane, Jackie Mason as The East River Creature and Creator/StephenFry (again) as Murray Bost Henson.
* Creator/{{Hipgnosis}}: Did the cover art for the British releases of the soundtrack albums.
* RealSongThemeTune: The theme for the radio show was a snatch of the Music/{{Eagles}}' "Journey Of The Sorceror", an instrumental from their 1975 album ''One Of These Nights''. It would be re-orchestrated for the TV series.

!![[Series/TheHitchhikersGuideToTheGalaxy TV Show]] trivia:
* HeyItsThatGuy:
** Creator/PeterDavison (who at the time was married to [[Characters/TheHitchhikersGuideToTheGalaxy Sandra Dickinson]]) as a creature that wants you to eat it!
** And [[Series/DoctorWho the Black Guardian]] was the voice of Deep Thought.
** [[WesternAnimation/CountDuckula Igor]] was Garkbit the Waiter.
** [[Franchise/StarWars Darth Vader]] is Hotblack Desiato's bodyguard, and is responsible for his body. (David Prowse wore the Vader suit in Star Wars, but didn't do the voice.)
** Slartibartfast [[Film/AHardDaysNight disapproves of the Beatles]].
** [[Film/AClockworkOrange P.R. Deltoid]] is the captain of the Golgafrincham B Ark.
* PropRecycling:
** The background characters in the restaurant at the end of the universe are equipped almost entirely with costumes recycled from earlier episodes, and in particular from the various Guide entries, thus helping justify the expense of items which otherwise would have appeared on screen for only a few seconds each.
** A badge from one of the Golgafrincham hats would be worn by [[Series/RedDwarf Arnold Rimmer]].
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