"The "Parallel Worlds" concept is the key to the STAR TREK format. It means simply that our stories deal withplant and animal life,plus people, quite similar to that on earth.Social evolution will also have interesting points of similarity with ours." —Gene Roddenberry in his pitch forStar Trek

While distant planets in fiction are typically different from Earth in many ways (see for examplePlanet of Hats,Genericist Government,Single Biome Planet), they also exhibit astounding cultural similarities:aliens tend to speak English in theidiom of a 21st-century speaker of English, their written language, numerals and methods of time measurement are conveniently identical to Earth standards or can be easily converted. You might even spot European cars orVancouver landmarks. Women will have Latin-sounding names ending in-a,^[1] wear their hair long and their heels high. Expect to come across proper names imported from Earth.

TheseInexplicable Cultural Ties are caused by the fact thatMost Writers Are Human and can reasonably expect you, the viewer or reader, to be human as well. Hence, some cultural similarities might be consideredAcceptable Breaks From Reality (like aTranslation Convention) or result from a limited budget. Othersmight strike you as avoidable mistakes by the creators of the fictional work.

This trope comes in vastly varying degrees. Sometimes it's just a tiny detail that catches the viewer's eye, maybe a building in the background you recognize fromReal Life or a visibly branded over-the-counter prop. On the other side of the scale, the alien planet will exhibit so many implausible similarities with Earth that yourWilling Suspension of Disbelief is shattered almost instantly. Extreme cases lead toSpace Romans. Also, the similarities might beHidden in Plain Sight, like a combination of social conventions that are inconspicuous precisely because they are so Earth-like but whose exact re-enactment on a distant planet is completely illogical. As this anOmnipresent Trope forScience Fiction, you might have become desensitized to it. And don't expect the characters on screen to spotInexplicable Cultural Ties for you - odds are they're crazyFunctional Genre Savvy. Instead, consult yourfridge frequently.

It's difficult to avert this trope completely in live action settings for budget reasons alone, although good writing can help to pull it off. Actually, as the above quote from the originalStar Trek pitch shows, use of this trope used to be a selling point to make live actionScience Fiction feasible for the small screen and pull someAesops in aLike Reality Unless Noted setting. Since then, this trope has lost some credibility due to the rise ofharder science fiction and better production values and techniques conspiring to change viewer's expectations. It is something of anUndead Horse Trope, though. Of course, the whole trope is conveniently avoided in case ofAliens Steal Cable orAbsent Aliens.

Animated Adaptations andComic Book Adaptations have the potential to shift a hitherto live action franchise towards visually more alien settings, they still need good writing and design to avoid this trope. Conversely,Live Action Adaptations of animated works or comic books are likely to introduce moreInexplicable Cultural Ties to a fictional world.

Cultural counterpart to the evolutionaryHuman Aliens andAll Planets Are Earthlike, which refers to planetary properties. See alsoFantasy Counterpart Culture

Anime andManga

• Exaggerated bySpace Adventure Cobra: The Animation, which starts with a story where Cobra eventually has to get into planet Galon, which has been isolated for 1000 years, and stop it from crashing into the sun. 1000 years notwithstanding, it has the same language, same architecture, names like Garcia, dark alleys with brick walls, earthlike clothes including hats with brims and jackets for the crooks, earthlike bars, and English writing everywhere.

Film

• Averted byOrwellian Retcon in aA New Hope where the Death Star's English tractor beam controls have been translated intoAurebesh for the current release.
  • InStar Wars Inexplicable Cultural Ties is often played with in the blatantlyMeaningful Names some characters are given, one of the worst offenders being Separatist general Whorm Loathsom. Sith names like Maul and Bane apply, too. The implication is that these names just happen to be meaningful in English or Latin by chance, while the in-universe language "Basic" justappears to be English on account of aTranslation Convention.
    • Likewise, different accents and dialects of English are used to distinguish characters' affiliation, background or species to the point that a British actor inThe Empire Strikes Back was given an American accent in post to conform to the Rebel-American, Empire-British pattern.

Literature

• Often played straight in classicScience Fiction novels and short stories, whereLike Reality Unless Noted is in effect, for example inNightfall byIsaac Asimov.
  • Old advice on writing science fiction usually encourages this; it might seem more exotic for alien characters to say "The podnaug is chatnik forgs away, we'll take the whekk", but that's just going tobreak the reader's immersion as they have to pore over your glossary. As you'retranslating the rest of the words anyway, you'd be better off just writing "The airport is fifty miles away, we'll take the car."
  • Philip José Farmer'sDayworld books have a minor example of this: he writes in the foreword that the future world depicted has universally adopted themetric system and the twenty-four hour clock, but Imperial measures and 12-hour time are used for the convenience of the reader.
• Deconstructed inUrsula K. Le Guin's noveletteThe Pathways of Desire, where more and more suspicious resemblances to American stereotyped notions of "primitive" tribes turn up in theHuman Aliens' culture. In the endthe adolescent fantasies of a boy back on Earth turn out to havecreated the entire planet.
• The Lord of the Rings: At chapter 1, a dragon is compared not only to atrain, but anexpress train:

The dragon passed like an express train, turned a somersault, and burst over Bywater with a defeaning explosion.

• InThe Hitchhiker's Guide to the Galaxy, every culture in the universe has an alcoholic drink that that sounds likegin and tonic. Inexplicability is the norm in theGuide, natch. Sadly for Arthur, this beverage similarity doesn't apply to tea.

Live Action TV

• The originalStar Trek was very aware of this trope (as evidenced by the opening quote) but played it straight most of time. The episodeBread and Circuses actuallyhandwaved it, citing something called "Hodgkin's Law of Parallel Planet Development", an alternative title for this trope.
• Zig Zagged in the newBattlestar Galactica. You see,all of this has happened before, all of this will happen again, includingVancouver, vintage Earth cars and army trucks,Classical Mythology, proper names,Bob Dylan...
• Mostlyaverted onBabylon 5: the variousRubber Forehead Aliens' home worlds are usually pretty alien, especially Minbar. The Centauri, however, qualify aspre-revolutionary absolutist space Frenchmen.
  • The Centauridress like Bourbon Frenchmen. Theybehave like Renaissance Italians.
  • The hat of the Minbari is tradition, and much of their behavior could be compared to a somewhat idealized(discounting that wholeKill All Humans thing, of course) version of several human cultures. It is their architecture that is alien rather then their culture.
  • Lampshaded when G'Kar mentions that, with no explanation that he has ever been able to determine, every sentient race in the galaxy has, apparently independently, come up with a dish that looks, smells, and tastes identical to what the Narn call "breen" and humans call "Swedish meatballs."
• Justified in theStargate Verse by means of anAncient Astronauts premise.
• Doctor Who oftensreferences many very different and alien worlds, but the ones we usually see seem pretty Earth-like,mostly due to budget reasons. Particularly of note is the Doctor's home world of Gallifrey, and the species seen in "Voyage of the Damned"; for a group coming to visit Earth's "strange and foreign culture" they certainly seemed like the British upper class.

Web Comics

• InHomestuck, thetroll civilization of the planet Alternia displays a staggering similarity to ours, notably in culture—they even havethe same TV shows and aWill Smith. Justified, however, in thatour universe (and thus Earth) were actually created by trolls, implying that the similarities are a result of humanity having vague memories of their makers' civilization and replicating them.

Western Animation

• Futurama plays with every kind ofScience Fiction trope. This one is no exception:
  • Played for Laughs with the Yiddish-using Decapodians.
  • Inverted byGeorge Takei's George Takei inWhere No Fan Has Gone Before: "I've done enough conventions to know how to spellMelllvar."Star Trek, of course, is possibly the chiefTrope Codifier.

• Trope
• Tropes in Space
• Otherworld Tropes
• Speculative Fiction Tropes
• Inexplicable Cultural Ties