One Degree of Separation

""Wanting connections, we found connections -- always, everywhere, and between everything. The world exploded in a whirling network of kinships, where everything pointed to everything else, everything explained everything else...""

- Umberto Eco, Foucault's Pendulum

Say one day you meet a girl and fall in love. Nothing wrong with that. However, on your wedding day, when you meet her father, you remember that he's the guy who failed you in biology in the twelfth grade. Okay, odd, but not inconceivable. But wait, isn't her mother the one who sat next to you at a bus station five years ago and gave you great life advice? And her cousin looks familiar, too. Hold on, it seems you've met her entire family at one point or another throughout your entire life.

And then she comes up to you and reveals that she's met your whole family before as well. In fact, you are her father's brother's nephew's cousin's former roommate. It seems there's only One Degree of Separation.

This is where every character is tangentially connected to almost every other character. It doesn't matter if it's an Easter Egg or important to the Myth Arc. Everyone's connected. In film this is known as "hyperlink cinema". This concept is also used by actors with a Bacon number (how many degrees away an actor is from Kevin Bacon) and by mathematicians with an Erdos number (how many degrees away from you is the Hungarian mathematician Paul Erdos). There's even a Bacon-Erdos for those rare few who've happened to both act in a film and written a mathematical/scientific paper. (e.g. Natalie Portman, who has an Erdos number of 5 and a Bacon number of 1, for a B-E number 6. Danica McKellar is also 6 (4 and 2). The late Stephen Hawking was a 7, BTW.)

Often part of a Jigsaw Puzzle Plot. Sometimes just a lot of Contrived Coincidence. See also Generation Xerox and Ah, You Know Him. Gets much more complicated when you have Loads and Loads of Characters who all seem to know each other. Or if they don't they quickly do thanks to You ALL Share My Story. Can be seriously aggravated by the presence of immortals.

Subtropes:
 * Already Met Everyone
 * Everyone Is Related
 * Everyone Went to School Together

Anime and Manga

 * The anime Code Geass, about a disowned prince rebelling against an empire, despite its incredibly large cast, features a great degree of connectedness. The protagonist, Lelouch, has more half siblings than he can count (since his father is an emperor with 108 wives), at least five of which are important to the plot. His father is the primary villain of the series. He and his sister spent time, as children, in the Kururugi household, giving him a personal relationship with his rival, an important businessman, a legendary general, and a girl who will later become an enthusiastic fan of his alter ego. The president of the student council at his school is from a noble family that were supporters of his mother. A military officer he disgraces turns out to have formerly been a guard at his mansion. A Japanese citizen who becomes an important supporter of his rebellion turns out to have been his maid, and also a ninja.
 * One of Lelouch's subordinates was romantically involved with an enemy knight, who just happened to be the first person to survive Lelouch's Mind Control powers in the beginning of the series, and the enemy knight had amnesia for a while after being shot by a high school girl who had a huge crush on Lelouch. His head scientist was a former colleague of an influential enemy scientist, who is both the mentor to Lelouch's aforementioned rival, and the fiancé of the head of the student council. Lelouch's primary accomplice and confidante was formerly the head of a cult whose members are now supporting the evil empire, and had watched over Lelouch when he was a child. Recently, a powerful knight in the empire was revealed to have had some sort of past connection with Lelouch. Also, a new rival of Lelouch's is a general in the Chinese Federation, who has pledged his life to support a child Empress whose first and only friend is the aforementioned fangirl of Lelouch's alter-ego.
 * Still, Code Geass isn't really any worse than any other series. The half-sibling thing is important to the plot of the first season, but it's not like their relationship is a coincidence. The rivalry between Lelouch and Suzaku's alter egos and their relationship several years beforehand is also pretty intentional, but closer. The real web of relations come towards the end, when we find out that several characters were in the home of, around, or had some business with Lelouch's mother.
 * Gundam Seed: In the first episode, Kira finds himself opposing Athrun, his best friend from the colonies. But before that, he runs into an unknown girl who later joins the crew of the Archangel—Cagalli.  Later on, the Archangel comes across an escape pod from a destroyed ZAFT vessel, containing none other than Lacus Clyne, Athrun's fiancee.   And their Ace Pilot, Mwu la Fllaga, has an ongoing feud with Athrun's commanding officer, Rau le Creuset,
 * It seems that in Ef: A Fairy Tale of the Two., everyone is tied to each other through their past and present. Episode 10 of a tale of melodies best emphasizes this, as nearly the entire cast comes up in name or on screen.
 * Almost all of the main characters in Chrono Crusade are connected to Chrono in some way, and through him to each other. Chrono met Rosette and her brother, Joshua, when they woke him up from a long sleep in a tomb. Joshua was then kidnapped by Aion, Chrono's former friend. Chrono and Rosette join the Magdalan Order to try to find Joshua based on advice from Father Remington, a man who was trying to convince Joshua to join the Order because of his powers. Remington was also During their search for Joshua, Chrono and Rosette run into Azmaria, who has powers startlingly similar to Joshua . They all start to look for Joshua together, and run into a "jewel witch" named Satella. Satella is searching for a missing family member, and finds out that  Pretty much the only characters that don't have a strong connection to Chrono, Rosette or Aion are Sister Kate (Rosette's commander in the Order) and Father Gilliam, an ally of Chrono and Rosette's in the order.
 * The characters in Bakuman｡ are getting this way around Kawaguchi Taro.
 * Paranoia Agent has this for the first few of Shonen Bat's victims. The victim Shougo is running against the third victim (Yuuichi) for student council president. Yuuichi is being tutored by the fourth victim (Harumi), who has an alter ego Maria that works as a prostitute, and one of her clients is the  victim Hirukawa. Hirukawa's daughter Taeka is the fifth victim.
 * All over the place in Dennou Coil. The grandfather of protaganist Okonogi Yuko "Yasako" Asazawa Yuko "Isako" and also  the Dennou Coil and 4-4-2-3, which gave Yasako and Isako their nicknames. Yasako's grandmother Megabaa (wife of said grandfather) set up the Coil Detective Agency whose membership includes that of  Tamako, whose immediate superior is  Nekome and is the aunt of Agency member Haraken, who was friends with Kanna, who died in a car accident  Takeru became friends with Yasako.
 * In Ichinensei ni Nacchattara, the main character Iori just happens to have his life saved by the sister of his oblivious crush, at the cost of being turned into a seven-year-old girl, which causes him to be sent to the same school as the kid whom he risked his life to save. By pure coincidence, his younger sister attends that school as well. He winds up living with his crush (who happens to bear a strong resemblance to ) and her sister, and after   his real family takes them in out of the goodness of their hearts, still completely oblivious to Iori's true identity. Also, a minor character that Iori and his friends encountered once lives in the same apartment complex.
 * The Black Jack anime suffers from this. Kumiko is the daughter of Jack's mentor Dr. Honma, and she works for a man named Tetsu who In the manga none of these characters are related.
 * At the beginning of Elfen Lied, Lucy escapes imprisonment but is shot and falls into the ocean. She happens to wash up on shore at the same town she lived in as a child, right when the boy she had a deep and ultimately tragic friendship with has moved back to town. And he just so happens to be taking a walk on the same stretch of beach at that very moment.
 * Durarara!!: Everyone—no, really, everyone—knows Mikado somehow. Leader of the Yellow Scarves?  Saika?   Urban legend Dullahan on a motorcycle?  ; the other is Orihara Izaya. And Harima Mika, , sits behind him in class.
 * Durarara!!: Everyone—no, really, everyone—knows Mikado somehow. Leader of the Yellow Scarves?  Saika?   Urban legend Dullahan on a motorcycle?  ; the other is Orihara Izaya. And Harima Mika, , sits behind him in class.

Comic Books

 * There is a part of Sin City where almost every protagonist is in a strip club, dancing or watching the dancing.
 * Which is more of a Continuity Nod, since the same scene is shown from different character viewpoints in different stories where they all happen to converge on this one time and place in Kadie's Bar. Sin City is full of similar scenes connecting two or more stories at the same time/place but different perspectives.
 * Marvel's recent Ultimate Origins mini series appears to be their attempt at doing this for the Ultimate Marvel Universe.
 * Of course in this case it makes no logical sense whatsoever. For example:.
 * Quite frankly, anything and everything Bendis established in Ultimate Marvel Team-Up was either retconned away or blatantly ignored almost as soon as the series was published. Even Bendis himself pretty much ignored everything.
 * The Marvel Comics universe includes a concept called the "Nexus-Being" or some such, which describes the person who is the focus of their universe. That role is filled by the Scarlet Witch: her father's a mutant Super Villain, her ex-husband is a robot superhero, her brother married into the royal family of a secret city that was Touched by Vorlons, and she got inbuilt magic powers from a Chaos demon. Combine her family tree with the Summers' Tangled Family Tree and you've half the goddamn 'verse.
 * Her family tree is connected with the Summers: Her sister Lorna is dating Havok, Cyclops' brother.
 * Jenny Sparks from The Authority was the spirit of the 20th Century, and as a result is somehow connected to every mover and shaker of the century, both good and bad—from being raised by Einstein to persuading Hitler to give up painting, and met or worked with pretty much every superhero on the planet. Her successor, Jenny Quantum, will presumably be the same for the 21st century.
 * Seems to happen to most of the mortal side characters in Sandman, even excluding circumstances directly caused by Morpheus' influence.

Film
""Also, they all seem to be sleeping with one another.""
 * In Saw, two apparent strangers, Adam and Dr. Lawrence Gordon, are trapped in a room together. It turns out, however, that ; this was all part of the plan, but the characters didn't know that when they found out.
 * The View Askewniverse, often with Jay and Silent Bob being in the center of the Venn Diagram of character connections. Jay and Silent Bob Strike Back is built off of all the characters from the previous films.
 * Star Wars. Not only is the Evil Overlord whom the main character met through a long series of coincidences his father, but the woman that he happened to meet through the same series of events is his sister.
 * In addition, it turned out that R2-D2 was owned by Queen Amidala and C-3PO was built by Anakin Skywalker. Boba Fett, as well, is the clone-son of Jango Fett, who is the original model for the entire Clone Army.
 * And Chewbacca also knew Yoda from the Battle of Kashyyyk near the end of the Clone Wars.
 * One review mentioned Vader's saying "I sense something..." when he first encounters the Millenium Falcon. No kidding: his son, his mentor, the droid he built and another from his past are aboard. He'd really be losing his touch with the Force if he couldn't pick up on all that.
 * Also, in The Empire Strikes Back, Darth Vader and Boba Fett share a brief exchange ("No disintegration." "As you wish.") In Attack of the Clones, Mace Windu kills Jango Fett while rescuing Anakin Skywalker, along with Obi-Wan and Padme, and then in Revenge of the Sith, Anakin kills (or assists in killing) Mace. So, Boba's dad died because of Vader, but Vader then killed the man who killed his father.
 * The 1989 Batman movie decided that having The Joker threatening everyone in Gotham City wasn't enough of a reason for Batman to hate him, so.
 * They did the same thing with the Kingpin in the Daredevil movie. And Quill in The Phantom movie (although he was only The Dragon). And Sandman in Spider-Man 3.
 * Clue uses this, with characters turning out to be increasingly connected as the plot unfolds; the precise nature of some of these connections, however, depends on which ending you go with.
 * Crash, which drew some criticism for it.
 * In Babel, connections are pretty one-way, and flimsy, but they're there, dammit, and it's meaningful. Oscar, please.
 * Parodied and Lampshaded in Burn After Reading:


 * Amores Perros (or Love's A Bitch) has three different stories with the characters tied together by a car crash and a dog.
 * Love Actually does this with a very large cast.
 * In Playing By Heart, this is The Reveal—except for some Arc Words, there's no hint of any connections other than the obvious ones, until the end.
 * Gosford Park—it's the motive for the murder.
 * Auf der anderen Seite/The Edge of Heaven by Fatih Akin did this with three parent/child pairs. All six characters were connected in some way.
 * Parodied in a scene in Hot Shots, where it turns out everyone in the barracks is related in some way.
 * Also parodied in the sequel (as a type of sequelitis). Topper is sent on a special mission to Iraq where his contact happens to be his former love interest Ramada (who was a psychologist in the previous movie) and one of the prisoners they're there to save is her husband. Also, while Topper's new love interest being on the mission doesn't fit this trope as this is how they met, her having been Ramada's college roommate does.
 * Also parodied in the revealed background between Saddam Hussein and President Benson. Given Benson's military background and involvement in the Iraq operation of the previous movie, its not inconceivable that they could have met, but when they whipped out lightsabers and began dueling, theres no doubt they were parodying this trope again.

Literature
"Zaphod: Is this going to happen every time we use the Improbability Drive? Trillian: Very probably, I'm afraid."
 * Les Misérables. Would you believe it, Cosette, we just happened upon the same convent of which I had saved the gardener's life? And your boyfriend, what a coincidence, feels obliged to fulfill a debt owed to the same family that abused and starved you for three years! And that same family produced that gamin on the streets who's taking care of his brothers who were supposed to go live with your boyfriend's grandfather and mon dieu let's talk about the Parisian sewers.
 * And then the barricades, where every surviving character fit for battle (and a few who aren't, like Valjean (seventy-two going on eighty) and Eponine (starving, lovesick, homeless and female)) shows up either during the battle or in the sewers.
 * Also happens in The Hunchback of Notre Dame. Victor Hugo liked this trope!
 * Tess of the D'Urbervilles (this was very popular around Hardy's time period.)
 * Robert A. Heinlein's short story All You Zombies:
 * Another Heinlein story, By His Bootstraps, uses almost exactly the same gimmick.
 * In The Cat Who Walks Through Walls, it turns out that the guy needed to save the multiverse just happens to be.
 * The Niven & Pournelle novels Lucifer's Hammer & Footfall. The later one was particularly egregious in this regard. Justified in Niven, Pournelle, & Flynn's Fallen Angels as many of the characters are connected through science fiction fandom.
 * In Escape From Hell (the sequel to Larry Niven and Jerry Pournelle's Inferno) every other person Allen Carpenter meets is someone he met in the previous book, or someone who's met one of those people, or both.
 * The Wheel of Time books: Elayne and Gawyn are introduced as siblings, Galad as their half-brother. Whose father, Taringail Damodred, is a relative of Moiraine Damodred (whose cousin, Caraline Damodred, also appears in the series). Galad's mother, Tigraine Mantear, on the other hand, is . Meanwhile, the mother of Elayne and Gawyn . Gawyn is now (sort of) romantically involved with Egwene al'Vere, who was Rand's love interest back in the first three books, while Rand is now involved with Elayne.
 * That's just scratching the surface. In this series, They All Share The Story. The mariner Bayle Domon, for example, helped Rand and Mat escape monsters in book one, helped Elayne and Nynaeve hunt the Black Ajah in book four, and traveled with Mat in books eight through 12 or so. None of their meetings were planned, and were barely even voluntary. The Mole who threatened Moiraine in book two also spied on Elayne and Nynaeve in later books. Verin mentored Elayne, Nynaeve, Egwene, Mat, Perrin and Rand, but each in different ways and for different reasons. Character histories like that are completely typical in this series.
 * Happens in Incarnations of Immortality, by the end of the series. Greatly assisted by the presence of several "temporary immortals" (the longest-lived being Parry) and a literal Fate playing a centuries-long chess game against the Devil.
 * The focus of Dirk Gently's Holistic Detective Agency, hence the "holistic" in the title—everyone is connected through the main character Richard. Which only goes to prove that Dirk's ideas about the interconnectedness of all things are not crackpot theories, despite the cynical use he makes of them.
 * Near the beginning of The Hitchhiker's Guide to the Galaxy (notice the pattern?), Ford and Arthur end up on the Heart of Gold and meet Trillian and Zaphod. Despite being, respectively, the only three survivors of and the President of the Galaxy, they all know each other already: Ford and Zaphod are old friends from the same star system, Trillian (originally Trisha) recently dumped Arthur for Zaphod at a party, and Ford knew about Trillian through Arthur.


 * Every single case of The Hardy Boys would somehow turn out to be connected to the one their father was investigating. This was dropped entirely for later series.
 * The Star Trek novel series The Rise And Fall of Khan Noonien Singh involves at least one character from almost every Star Trek episode with characters from the 20th century. Khan (of course), Gary Seven and Roberta Lincoln, Jackson Roykirk, Shaun Christopher and Flint the Immortal from TOS; Guinan, Ralph Offenhouse and Clare Raymond from TNG; Jeffrey Carlson from Deep Space Nine; Rain Robinson and Shannon O'Donell from Voyager.
 * Gravity's Rainbow has a cast of several hundred characters, and at least for the 40 or so main ones it seems they are all interconnected in multiple ways. (Mapping it all out can be pretty difficult).
 * Great Expectations. Magwitch, the convict who Pip meets at the beginning, is Estella's father, and Compeyson, the other convict, is the former lover of Miss Havisham (who adopted Estella).
 * Also the lawyer Jaggers' housekeeper is Estella's real mother and the boy Pip fought with as a child turns out to be Herbert Pocket, who, as a young man, teaches Pip how to be a gentleman.
 * Dickens is the master of coincidence though. The titular character in Oliver Twist is saved from going to prison by the man who turns out to be the friend of Oliver's real father and an admirer of Oliver's mother, who died giving birth to him, though in the musical they simplified it and made him Oliver's grandfather.
 * Lampshaded in The Kite Runner. Amir is not surprised at all to discover that a random beggar on the street knew his mother. Apparently, in Kabul, every single person is related to everyone else somehow or other.
 * Sarah Dessen is known for this. All of her books seem to take place in one town, or in the beach town next door to it, and it must be a small area because in any one of her books (aside from the first) there will invariably be references to the others.
 * Examples include: Truth Squad (and Remy's) cameo in Just Listen; Jamie getting Owen from Just Listen to help him with Cora's birthday present in Lock and Key as well as Rogerson from Dreamland appearing (while briefly); Annabel and Owen from Just Listen seeing Macy and Wes from The Truth about Forever at the World of Waffles; and Cora from Lock and Key inviting Remy's mom from This Lullaby to her Christmas party. In Along for the Ride, Heidi is friends with Isabel and Morgan from Keeping the Moon and used to work at Last Chance Cafe.
 * Murder on the Orient Express. Almost everybody on the train knew each other by
 * In Dracula, the Count's lawyer's fiance's best girlfriend's ex-suitor's former mentor just happens to be Dr. Van Helsing, who knows how to kill vampires. Plus, he moves in practically next door to the ex-suitor's insane asylum. Granted, Whitby wasn't exactly a metropolis back then, but it's still a bit much...
 * And of course, it's a bit of a coincidence that the first person he targets is Lucy, that lawyer's fiance's friend, which is how Van Helsing actually gets involved.
 * The entire cast of Oliver Twist follows this trope as well.
 * The girl, Kendra, that Vince falls in love with in Gordon Korman's Son of the Mob just happens to be the daughter of the federal agent investigating Vince's Mob boss of a father.
 * Christopher Brookmyre novels have lots of subtle nods. Maybe one of the subtlest: the photographer in Not The End of The World is implied to have shot Simon Darcourt's band for their one single.
 * A Tale of Two Cities had every major character directly connected to either the Marquis St. Evrémonde or the Doctor he had imprisoned for no real reason. Charles Dickins is rather fond of this trope, isn't he?
 * In the Liaden Universe series, as a result of the Korval clan's Weirdness Magnet and Coincidence Magnet nature, many non-Korval characters find their paths crossing Korval's repeatedly in improbable ways. It sometimes seems as if every minor character in the entire universe is related to Korval in ways that just haven't been revealed yet.

Live-Action TV
"(Nathan and Matt arrive at Primatech Paper) Hiro: (seeing Nathan) Flying man! Matt: Who is this kid?"
 * Lost is the epitome of this trope. To give just one example:
 * Charlie played guitar outside the offices where Desmond had a job interview, who in turn once met Jack while jogging in a stadium, and Jack's father, Christian Shephard, is also, met , got drunk with , and that's all before he died. Word of God says that these are not Easter eggs, but rather a part of the larger mythology.
 * All the character connections are shown on this page, with two rather impressive graphics (go on, zoom them).
 * In Seasons 1-3 such connections only occurred every other few episodes. By the time of Season Six all pretenses are dropped and each episode features cross-character connection at a rate of about once every 15 minutes in the Flash Sideways.
 * Well, by the end of season 3, they'd
 * Heroes is a user of this trope as well, though to a lesser extent than Lost, with even some characters saying, "We're all connected."
 * Though the fact that many of the characters are the children of the founders of The Company or were manipulated by it this doesn't seem too implausible.
 * And the writers of doing a pretty good job of remembering that not everyone has met everyone. For example, it took two full seasons for Matt and Hiro to meet:


 * The same thing happens with Claire and Hiro, and they have a whole episode centering around it with lampshading of how they never met each other.
 * Though they sometimes slip up-like how Nathan in early season 2 seemed to have forgotten meeting almost everyone, even people he met before the events of the finale.
 * On a related note, the fact that new Petrellis keep cropping up certainly implies this.
 * Spaced has two flashbacks to childhood showing Tim being chased by a pack of dogs, (giving him a fear of them) and Daisy chasing after them. They don't make the connection. On the DVD Commentary, they mention plans to have all four main characters in the same park as children (with the fifth, Marsha, as a young mother) without meeting, but never did it.
 * Caprica: Joseph Adama, father of the future military leader of the surviving human race, knew Daniel Graystone, the inventor of the Caprican Cylons.
 * The Class did this. A group of eight adults who were in the same third grade class spontaneously be re-involved with each other lives, both intimately and in passing.
 * Six Degrees did the same with a more serious tone.
 * Misfits got hit with a boatload of this in the time-travel episode. Every character happened to have been at the same club on the same night, and several of them had brief encounters that they had presumably forgotten about the next time they met. This includes their social worker and his girlfriend, who became his fiancee that night, but he didn't have an engagement ring because Kelly and her boyfriend just so happened to break into their car and steal it.
 * Mad About You discussed this when Jamie got pregnant - they wanted to tell everybody in Thanksgiving, Paul pointed out it would be leaked and spread before the date because people they know usually know each other, using the Bacon numbers as a reference. And in the end of the episode, one person appears to congratulate on the pregnancy... Kevin Bacon himself!
 * In Friends, Chandler's connection to the group started off simply as "Monica's neighbour", but later it turned out that, when he was in college, he had also been Ross' roommate, and had met Monica and Rachel several times.
 * Phoebe, who first met the group through being Monica's roommate, also mugged Ross when they were teenagers.

Newspaper Comics
"Could it be that she was the sister of the boy in Kansas who loved the girl with the tattered shawl who was the daughter of the maid who had escaped from the pirates?"
 * In Peanuts, Snoopy attempts to tie together all of the characters in his novel "It Was a Dark and Stormy Night" in this fashion:


 * Linus then asks "What about the king?" and gets beaned with a typewriter.
 * Lampshaded in this Doonesbury strip, as shown in the page image.

Theater

 * Played straight, but almost to the point of parody in The Importance of Being Earnest by Oscar Wilde. Let me just see if I can get this straight: Algernon and Jack are friends from the city, Jack wants to marry Gwendolen, who is Algernon's cousin and the daughter of Lady Bracknell. That's all well and fine, but Jack has no biological parents (high society no-no), having been abandoned at a train station as a baby. It turns out that Jack's ward, Cecily, who is Algernon's love interest, is being taught German by Ms Prism, the former employee of Lady Bracknell and also the woman who accidentally abandoned Jack as a baby. It's then revealed that therefore Jack is Lady Bracknell's nephew, Gwendolen's cousin and Algernon's brother. Ironically this is one of the few times where characters turning out to be related actually leads to a happy ending as it gives Jack a respectable background.
 * Played straight in Wicked where every single character of relevance in the play can be tied to Elphaba. Not unreasonably so since she's the Wicked Witch, but let's sum up. Her teacher is the Wizard's Dragon, her sister is the Wicked Witch of the West, her manservant is a school chum, she saved the Cowardly Lion, the Scarecrow is her transformed boyfriend, the Wizard is her father, and so on and so forth.
 * Charleys Aunt: Jack is Sir Francis' son, Kitty's suitor, and Charley and Babbs' friend. Charley is Amy's suitor, Dona Lucia's nephew, and Jack and Babbs' friend. Babbs is Jack and Charley's friend, and turns out to be the young man who deliberately lost money to Ela's father playing cards when he was penniless and dying, and who loved and was loved by Ela. Sir Francis (Jack's father) turns out to also be Dona Lucia's old suitor. Dona Lucia is Charley's aunt, and Ela's guardian. Kitty is Sir Spettigue's niece; she and Amy are both under his legal guardianship, and are best friends. Sir Spettique wants to marry Dona Lucia. The only character who isn't related to, or in love with, at least one of the others is Brassett, Jack's valet.

Video Games

 * Final Fantasy VIII: It turns out that And all those flashbacks Squall was having to Laguna were facilitated by
 * And it doesn't even end there:
 * Phoenix Wright: Ace Attorney uses this to an extreme in the third and fourth games, particularly the third.
 * To demonstrate how bad it is: By the end of the third game's last case, Protagonist Phoenix Wright is pretty much the only relevant character who is not either related to  or was directly screwed over in a way by the events of DL-6, or both. And even then they indirectly had huge influence on his life by setting up 90 of the 100 reasons he decided to become a Defense Attorney.
 * In Knights of the Old Republic, Darth Revan, Big Bad Malak's former master, was also HK-47's original owner, the Jedi who inspired Juhani to join the Order, and the one who led the fight against the Mandalorians (including Canderous). He died in a capture mission led by Bastila.
 * And in the sequel, The Exile commanded Brianna's mother and Bao-Dur at Malachor V, a battle Canderous fought in on the other side, and ended it by using the Mass Shadow Generator, killing Mira's adoptive family, inadvertently creating Visas' master, and inspiring Revan to commission HK-47 so he wouldn't need such overkill in the future. She was also Michal's intended master before she ran off, so she's not only a dominant influence in the lives of everyone on that ship, she's also responsible for all their significant neuroses.
 * Jade Empire, also of Bioware, had several characters openly expressing their disbelief in the number of connections encountered. As it turned out, . Gah!
 * In Planescape: Torment, you come across a rather staggering array of people with one degree of separation from one or another of The Nameless One before he got amnesia, including all your party members . Mainly Justified in that the game is about a personal quest for identity and therefore you will logically be hunting down people with a prior connection to you, but many of the more incidental side-quests show a rather astounding array of this either way.
 * Infinity series:
 * In Ever 17, while nobody except Sara and You seem to have known each other beforehand, it turns out that As you can see from the majorly spoilery bit there, it's... complicated.
 * In Remember 11, Satoru, the person with whom Kokoro begins to swap minds just happens to be where she was planning on going before her plane crashed.
 * Fire Emblem. Holy cow there is a ton in every game, mostly revealed through optional conversations. Pretty much every game has had several pairs separated relatives or friends who both happen to join the same army and find each other.
 * The freeware RPG Last Scenario absolutely loves this trope, gradually revealing connections to a certain flashback of seemingly mild importance. At first we simply learn that Okay, given their current situations, they were bound to meet up again. But then we find out that
 * The Reveal near the end of Overlord invoked this. As it turned out.
 * In Hotel Dusk: Room 215, the main character (an ex-NYPD detective) stays at a dingy hotel in the middle of nowhere for one night. By morning, he's discovered that every single guest staying there that night is connected to either his former partner Bradley or to another guest in the hotel (and frequently both). This also goes for staff members.

Web Comics

 * In Questionable Content, Marigold, the owner of one of Pintsize's robot friends, who repairs Pintsize when he overloads himself, is the roommate of Angus, the guy who's always in Coffee of Doom trying to get insulted by Faye.
 * There was another case in which a girl asked Marten out (after he'd gotten with Dora), was declined, and went to Dora's coffee shop, where she found out. Dora goes Clingy Jealous Girl on Marten for not mentioning that he got asked out, and they argue about it, reconcile, and go out to dinner, where the girl is their waitress. A few strips later, Steve has an unrelated chance run-in with the same girl, and winds up trying to track her down before realizing what he was doing could constitute stalking; leaving the building he's in when he realizes that, he runs into her again. They're now dating.
 * Sluggy Freelance has way too many characters for them all to be connected, but there are many examples of completely random connections, especially between the different alternative realities. This is partly justified in that the dimensions are indeed parallel and often have many similarities, but only partly. Often it's more that the reader can notice the coincidences, not so much the characters, because different people meet different people.
 * As just one example, the story "Oceans Unmoving" featuring Bun-bun but none of the other main characters features several characters who have been blasted out of time itself, mostly by failed Time Travel devices. A later story shows how one of them got there in the first place and refers to another having got there the same way. Some other main characters see this, but they have no idea Bun-bun has encountered said people, and he himself isn't present at this time to notice the connection (and might not anyway).
 * At the end of the second volume the strip had a flowchart describing all the major characters and how they all interacted with each other, with Torg at the center. Everyone was one degree of separation from Torg.
 * Nearly everyone and everything in Homestuck is connected to some degree. Overlaps with Everyone Is Related and Tangled Family Tree.

Western Animation

 * Several in The Venture Bros. Rusty Venture, the Monarch, Baron Underbeiht, Pete White, Brock Samson and Mike Sorayama all went to the same college at the same time. We later discover that Brock and Hunter Garthers sent Billy Quizboy to spy on Professor Fantomas which resulted in the professor being turned into Phantom Limb. While at the college Dr. Girlfriend was one of Phamtom Limb's student. Richard Impossible was also a teacher at the college.
 * Another example is that the Monarch and Henchman 24 used to be a henchmen for Phantom Limb.
 * Another example is that Dermott the only kid that Hank ever befriends is his and Dean's half-brother.
 * Kim Possible's Arch Enemy Dr. Drakken was a college friend of her father. Tasked with finding dates for their friends, he built crude robot girls instead. The resulting mockery led to his Start of Darkness, storing up trouble for Dr. Possible's future daughter.
 * Phineas and Ferb... Perry's arch-nemesis is Professor Heinz Doofenshmirtz, formerly married to Charlene Doofenshmirtz, who goes to the same cooking class as Linda Flynn, Phineas and Candace's mother. Doofenshmirtz's daughter, wife, and himself have also met Phineas and Ferb (and Candace, besides Doofenshmirtz ) but Doofenshmirtz is still not aware that they are the owners of Perry. Doofenshmirtz also at one point dated Linda Flynn, and in one episode, he states that he wants to see her again.
 * And now, as of 'Fireside Girl Jamboree', Doofenshmirtz and Candace have met, as she delivered his cupcakes. Also, Doofenshmirtz's daughter Vanessa seems to be friends with Candace, and Ferb has a crush on her.
 * This occurs throughout Robotech as a way of tying together the different groups of characters in the different sub-series. Max Sterling and Miriya Parina, of the Macross cycle, eventually have two daughers: Dana and Maia Sterling, who star in the Robotech Masters cycle and The Shadow Chronicles movie, respectively. Likewise, Claudia Grant of Macross is eventually revealed to have a brother, Vince Grant, who is one of the stars of The Sentinels and who appears in The Shadow Chronicles along with his wife, and whose son, Bowie Grant, stars in the Robotech Masters cycle. Marcus Rush, another of the stars of The Shadow Chronicles, is the younger brother of Marlene Rush, a bit character in the New Generation cycle.

Real Life
"I was friends with Stan Getz, and Lionel Bart, who wrote Oliver! The painter Francis Bacon lived next door. He always tried to get me into his studio to paint me, but he was very gay and I thought, “I’m not going up there.” An actor called David Baron said he was going to write a play, and I said I’d act in it. He called it The Room and he did it under his real name, Harold Pinter. In the sixties, everyone you knew became famous. My flatmate was Terence Stamp. My barber was Vidal Sassoon. David Hockney did the menu in a restaurant I went to. I didn’t know anyone unknown who didn’t become famous."
 * The Roman Empire in the first century (AD or BC). Rome and I, Claudius get this down to a T. Not only are the entire aristocracy of Rome related six different ways, but they know, grew up with, nearly married, killed the brothers of (etc.) the rest of the important people in the ancient world.
 * May be Truth in Television, just because over the course of anyone's lifetime, they'll have plenty of these odd run-ins. Not quite as extreme as everyone being related to everyone else somehow. As they say, it's a small world.
 * By extension, the likelihood of such odd run-ins may be increased depending on the area. A city like London is not only very populous, but it also has a large number of tourists visiting each day. If you're from another area of the UK, there may well be other people from your hometown visiting (or even permanently residing in) London at the same time you choose to visit.
 * Bradocks expedition (French and Indian/Seven Years War 1755). In a force of a bit less than 2,000 men we have: The leader of the coming revolution AND the next two ranking generals (George Washington, Horatio Gates, and Charles Lee, the latter two in the British army at this time), the military govenor under whom said revolution blows up (Thomas Gage the vanguard commander). AND in the baggage train we have another future general (Daniel Morgan), and a future famous explorer (Daniel Boone) driving wagons. How has this not been made into a movie?
 * Try playing the handshake game - pick a person, and work out how many people whose hand you have shaken, or had similar interactions with, that it would take to connect you to that person. It's usually not a great deal more than six.
 * The paper suggesting that everybody is connected by no more than 6 degrees of separation is well known, but this troper is fond of a story connected to it. Professor's giving a presentation on it, and says that everybody is connected to everybody else by 6 degrees of separation. Joker in the back stands up and asks for the chain from the professor to Haile Selassie, Emperor of Ethiopia. Professor stutters that it doesn't quite work like that, when a gentleman in the front row stands up and says that he knows Haile Selassie, and he knows the professor. Two links in the chain. The joker sits down, properly chastened.
 * The professional sports version of this is a Sillinger number, after journeyman ice hockey player Mike Sillinger. No player in the National Hockey League's more than 90 year history is more than six degrees from Sillinger, and at one point in the 2007-08 season, every single player in the 30 team league had either played with Sillinger or had a teammate who had played with Sillinger. It's commonly believed that you can connect Sillinger to Kevin Bacon (here's how it works: Bacon was in "Sleepers" with Ron Eldard, who was in "Mystery, Alaska" with Tie Domi, who was on the Toronto Maple Leafs with Petr Svoboda, who was on the 1997-98 Philadelphia Flyers with Mike Sillinger), but in fact, the Petr Svoboda who played with Domi and the Petr Svoboda who played with Sillinger are different people. However, Domi was on the Toronto Maple Leafs with Eric Lindros in 2005-06, and Lindros played with Sillinger on the 1997-98 and 1998-99 Flyers. Sillinger's Bacon number is 4.
 * There is a similar chain-of-associations game for mathematician Paul Erdos. And just as with Sillinger and Bacon, there is an Erdos-Bacon Number.
 * If you are in a career with a small enough population of occupants, especially one where said people often get shuffled around to different locations (say, if you are a specialist in a small enough career field in the armed forces), you quickly find that everybody seems to know everybody else.
 * Michael Caine claims that everyone he knew as a struggling actor in London during Sixties ended up becoming famous like him: