Events in one series also impact continuity in another series. This is an element that may go into defining a [[TheVerse 'Verse]].

Immensely common in American [[ComicBookTropes comic books]], to the point where some series essentially merged into one during the '90s.

See also {{Crossover}}, {{Intercontinuity Cross Over}}, and {{Massive Multiplayer Crossover}}.
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!!Examples:

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[[folder:Anime/Manga]]
* In ''Franchise/{{Digimon}}'', after the events of ''Anode Tamer'' and ''Cathode Tamer'' for the Wonderswan - sorry, NoExportForYou - Ryo Akiyama dimension-hops to the ''Adventure'' universe. He witnesses the battle with Diablomon from the second movie and meets with Ken Ichijouji. Ryo and Ken defeated Milleniummon in ''Tag Tamers'' and Ken is infected with a Dark Spore, setting events in motion for ''Adventure 02'' and confusing the ''hell'' out of anyone who had to take Ken's flashbacks to those events at face value with no knowledge of the games. Later in ''Brave Tamer'', his partner Monodramon merges with Milleniummon resulting in Cyberdramon. Ryo then appears in ''Tamers'', a universe separate from Adventure, and he has Cyberdramon with him who is aggressive and uncontrollable due to Milleniummon's half of his being. So this is basically three (or more) very separate continuities all connected through Ryo.
** It should be noted that Ryo's movie and 02 scenes go unnoticed by American viewers because he resembles Wonderswan Ryo far more than Tamers Ryo because of the art style (even once Tamers Ryo leaves the Digital World and gets the shirt he has in Anode/Cathode.) Once you know what he looks like, there's no mistaking his movie and 02 flashback appearances for anyone else.
* All of KenAkamatsu's manga series seem to have this, especially ''LoveHina'' and ''MahouSenseiNegima''. Specifically, both LoveHina and {{Negima}} have identical characters named Mei, who appear to be the same person, WordOfGod states that the inn that Keitaro and Naru stayed at in LoveHina was the same inn that several characters from {{Negima}} stayed at, and the Shinmeiryu sword school is used by characters in both series. In a recent {{Negima}} chapter, Motoko's family name [[http://www.mangafox.com/manga/mahou_sensei_negima/c256/10.html was explicitly mentioned]] in relation to Shinmeiryu techniques, and a specific technique ("Zanmaken: Ni No Tachi") used in LoveHina has minor plot relevance in {{Negima}}.
** Negima also has a shout out to his first manga, ''Manga/AILoveYou'', when the subject of sentient A.I. comes up; it's hinted that part of [[RobotGirl Chachamaru]]'s programming may have been written by ''A.I. Love You'''s protagonist.
** [[http://vetus.wordpress.com/nazenani/#v30 Akamatsu himself]] has confirmed that the Nitta-sensei from Manga/AILoveYou and the Nitta-sensei from Negima are the same person, as well as the fact that [[LoveHina Motoko]] and [[MahouSenseiNegima Eishun]] [[http://vetus.wordpress.com/2010/09/02/vol-31-qa-partial/ are related somehow]].
* ''{{xxxHoLiC}}'' and ''TsubasaReservoirChronicle'' both merge at numerous times, and characters in one series are often seen in another. The anime for both series, due to unfortunate copyright issues, don't cross over as much.
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[[folder:Comics]]
* Clearly the {{Marvel Universe}}, which includes characters from the ComicBook/FantasticFour, Comicbook/TheIncredibleHulk, {{Spider-Man}}, ComicBook/IronMan, CaptainAmerica, Comicbook/GhostRider, The ComicBook/{{X-Men}}, ComicBook/ThePunisher and many more.
** A limited amount of this has appeared in the [[Franchise/MarvelCinematicUniverse recent Marvel movies]] -- Nick Fury appears at the end of Film/IronMan, and Tony Stark appears at the end of {{The Incredible Hulk}}. This crossover has, so far, not appeared in the Spider-Man or X-Men movies.
*** The lack of crossover with the Spider-Man and X-Men franchises are due to the film rights to those characters being owned by Sony and Fox, respectively, as opposed to Marvel Studios.
** Behind-the-scenes pictures of some of the maintenance panels on the X-Jet in X2 reveal that some systems were built by Stark Enterprises (and that there were no user serviceable parts inside!), but they're far too small to be seen onscreen. An "Intercontinuity Nod"?
* {{DC Comics}} has done this as well, like with Franchise/{{Batman}} and Franchise/{{Superman}}.
** At one time this was the exception rather than the rule... each story was set in its own continuity and it was rare for one costumed hero to even be aware that others existed. It wasn't until the Justice Society of America title in 1940 that heroes interacted with each other on a regular basis, and it proved so popular that DC eventually attempted to weave pretty much ''all'' its titles into a single overarching continuity (things that couldn't be made to conform were assigned to alternate universes in the "multiverse" concept, and it was possible to cross even those over if a writer really wanted to... the first such crossover involved Barry Allen and Jay Garrick (both "The Flash" in different universes).
* It's not uncommon for a main character in one ''SinCity'' story to play a minor role or even a cameo in a different story. Many stories have also been shown to happen at the same time, such as ''Hard Goodbye'' and ''A Dame To Kill For''.
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[[folder:Film]]
* The MarvelCinematicUniverse is one of the very rare movie examples; while all movies are self-contained, there are lots and lots of references to the other ones. Nick Fury has appeared in ''Film/IronMan'', ''Iron Man 2'', ''Film/{{Thor}}'' and ''Film/CaptainAmericaTheFirstAvenger'', while Tony Stark made an appearance at the end of ''Film/TheIncredibleHulk''. In The Avengers, the main characters from all the mentioned movies will join forces. Sadly, we're ScrewedByTheLawyers when it comes to anyone from the [[Film/{{Spider-Man}} Spidey]] or Film/{{X-Men}} films appearing, despite Wolverine and Spider-Man having been in Avengers comics for some time now and Beast having a long history with them.
** And now, of course, we have ''Film/TheAvengers'' tying it together, along with the TV Series ''Series/AgentsOfShield'', which tends to reference every movie that has occurred in the MCU, including movies that only came out a week before the episode containing the reference aired.
** ''Film/CaptainAmericaTheWinterSoldier'' had a ''huge'' impact on ''Series/AgentsOfSHIELD'', far moreso than any other movie in the verse, given that [[spoiler: the big reveal of ''Winter Soldier'' concerned HYDRA's infiltration of SHIELD.]]
* TheViewaskewniverse, TheVerse in which Creator/KevinSmith has set 6 films, several comic books, and an AnimatedAdaptation.
** Several characters will be heard about in one movie, only to be seen in a later film.
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[[folder:Literature]]
* In the [[Literature/HonorHarrington Honorverse]] the novels ''Ashes of Victory''/''Mission of Honor'', ''Crown of Slaves''/''Torch of Freedom'' and ''Shadow of Saganami''/''Storm from the Shadows'' all take place concurrently, so we get three different looks at the same sequence of events, and often have entire chapters duplicated across books.
* In the ''DragonridersOfPern'' novels, the events of ''Dragonquest'', the second Lessa novel, affect the events of ''Dragonsinger'', the second Menolly novel. Also many other cases, since all the Pern novels are explicitly set in the same universe and it's very common for the main characters in one novel to be minor characters in another and for there to be considerable chronological overlap (''Dragonquest'' and ''Dragonsinger'' cover roughly the same time period as experienced by two different people). This is complicated even more by the (somewhat risky) draconic ability to time travel.
* All of {{Brandon Sanderson}}'s adult novels (''Literature/{{Elantris}}'', ''Literature/{{Mistborn}}'', ''Literature/{{Warbreaker}}'' and ''Literature/TheStormlightArchive'' so far, with others forthcoming) are set in the same universe, with at least one character (Hoid) appearing or being referenced in every one, and hints of a broader MythArc on the horizon.
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[[folder:Live Action TV]]
* ''Series/{{Star Trek|The Original Series}}'' did this as well when ''[[Series/StarTrekDeepSpaceNine Deep Space Nine]]'', ''[[Series/StarTrekVoyager Voyager]]'', and ''[[Series/StarTrekTheNextGeneration The Next Generation]]'' films were all running at the same time.
** Miles O'Brien passed over to ''Deep Space Nine'' in its pilot episode. After the destruction of the ''Enterprise'' in the ''[[Film/StarTrekGenerations Generations]]'' movie, Worf joined the station as well. The Deep Space Nine crew changed uniforms after ''[[Film/StarTrekFirstContact First Contact]]''.
** This also meant that Worf's presence in the movies following ''Generations'' had to be continuously HandWaved, as he was not assigned to the Enterprise-E.
** There is an entire episode of ''[[Series/StarTrekVoyager Voyager]]'' where the destruction of the Maquis by the Dominion/Cardassian alliance over in ''[[Series/StarTrekDeepSpaceNine Deep Space Nine]]'' was a key part of the plot.
* ''Series/BuffyTheVampireSlayer'' and ''Series/{{Angel}}'' interacted so much during their respective fourth and first seasons that watching them in concert is almost a neccesity to understand what's going on in either.
* There is ContinuityOverlap between the last seasons of ''Series/StargateSG1'' and the start of ''Series/StargateAtlantis'', as well as between the end of the fourth season of ''Series/StargateAtlantis'' and the ''Film/StargateContinuum'' movie.
* The new series of ''Series/DoctorWho'', ''Series/TheSarahJaneAdventures'' and ''Series/{{Torchwood}}'' have the occasional continuation between them. For example, the Sontaran invasion in ''Doctor Who'' leads to a stranded Sontaran soldier in ''The Sarah Jane Adventures''.
* Bryan Fuller's works -- ''DeadLikeMe'', ''PushingDaisies'' and ''{{Wonderfalls}}'' -- are all apparently set in the same universe. PushingDaisies and {{Wonderfalls}} share a character (a one-timer) and PushingDaisies also refers to Happy Time Temp Agency, which is where George worked in DeadLikeMe.
* ''Series/{{Friends}}'', ''{{Mad About You}}'' and ''Series/CarolineInTheCity'' are all in the same universe, although they don't have a major impact on one another, just cameos by characters in each work.
** ''{{Seinfeld}}'' also exists in this universe (Paul Buchman was the original owner of Kramer's apartment), which is weird because George's fiancee, Susan, enjoys watching ''{{Mad About You}}''.
* ''Series/{{CSI}}'' hosted the PoorlyDisguisedPilot of ''CSIMiami'', which in turn ''CSINewYork'' launched from, so the teams exist in the same universe, and even a killer that was featured first in Miami was caught in the NY show.
* Similary, ''{{JAG}}'' spawned ''Series/{{NCIS}}'' which spawned ''Series/NCISLosAngeles''. Other than the PoorlyDisguisedPilot, there was one minor cross-over of a JAG lawyer appearing on NCIS. Abby Sciuto is the only character on either of the three to appear on all three shows.
* The entire ''Franchise/LawAndOrder'' universe, with guest appearances by many actors on other shows.
** ''Series/HomicideLifeOnTheStreet'' had a few cross over episodes with ''Law & Order''.
** Detective JustForFun/JohnMunch (Richard Belzer) started out on ''Homicide'' -- and has also played the character in no less than eight different shows, for at least four different networks.
*** and he appeared in [[Film/AVeryBradySequel the Brady Bunch sequel]].
* The SyFy Channel's played this game, with crossovers between ''Series/{{Eureka}}'', ''Series/{{Warehouse 13}}'', and ''Series/{{Alphas}}''.
* When Bobby Ewing was killed off on ''Series/{{Dallas}}'', it was mentioned in SpinOff ''KnotsLanding'', and Gary Ewing named his newborn son after his late brother. After the infamous ''AllJustADream'' ResetButton that brought Bobby back, ''Knots Landing'' stopped referencing its parent show.
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[[folder:Web Comics]]
* {{Megatokyo}}'s Junpei has shown up in {{Applegeeks}}, and they cross over from time to time. Mostly though, they stay apart, mainly because one set of characters in in Japan and the other is in America. Plus, time passes much slower in ''Megatokyo'' than in ''Applegeeks''.
[[/folder]]

[[folder:Web Original]]
* Almost all of the WhateleyUniverse stories take place among a small group of kids who go to [[SuperheroSchool Whateley Academy]] together, so there's phenomenal amounts of Continuity Overlap, to the point that it looks like the authors have to coordinate character schedules down to the day.
[[/folder]]

[[folder:Video Games]]
* All of Volition's games take place in the same continuity, where the SaintsRow series serves as a prequel to the RedFaction series, taking place TwentyMinutesIntoTheFuture. Volition no longer have the rights to the FreeSpace series, but a "Subach Industries" shows up in SaintsRow, referencing the Subach-Innes corporation from the former.
* Valve's ''VideoGame/{{Half-Life}}'' and ''VideoGame/{{Portal}}'' videogame series canonically exist in the same universe.
** ''VideoGame/{{Portal}}'' was introduced in the "Orange Box" compilation as a GaidenGame borrowing elements of the ''Half-Life'' universe -- specifically, it mentions Black Mesa as a competitor to Aperture Science for government funding, and WordOfGod says that [=GLaDOS=] awakening and subsequently [[AIIsACrapshoot going berserk]] coincided with the Combine invasion of Earth, preventing the scientists from getting help.
** ''VideoGame/{{Half-Life 2}}: Episode 2'', for its part, introduces a ship called the Borealis as a major plot element; said ship was built by Aperture as part of an early teleportation experiment and "vanished, along with part of the dry-dock".
** ''VideoGame/{{Portal 2}}'' continues the gag with an EasterEgg where you actually find the other part of the dry-dock, complete with a life preserver labeled "Borealis", and Cave Johnson directly mentions Black Mesa in the [[PosthumousCharacter pre-recorded messages]] you find in Old Aperture.
* ''Franchise/StreetFighter'', ''VideoGame/FinalFight'', and ''VideoGame/RivalSchools'' are all in the same universe. Several characters from ''Final Fight'' have become a regular part of ''Street Fighter'', most notably Cody, Guy, and Rolento, and Sakura was playable in the first ''Rival Schools''. Since ''VideoGame/SaturdayNightSlamMasters'' is in the Final Fight timeline (Haggar is in the cast, and canonically it's what he did before he became mayor), that puts it in the same setting as well.
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