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* ''FanFic/ADarkKnightOverSinCity''. It's rather obvious what it is about, going by the [[ExactlyWhatItSaysOnTheTin title.]]
* In the ''WesternAnimation/JackieChanAdventures'' and ''WesternAnimation/TeenTitans'' crossover fanfiction ''Fanfic/AShadowOfTheTitans'', Jade ends up in the Teen Titans universe.
* In ''Manga/YuGiOh'' fandom there's ''Blog/AskDarkHourBakura'' which is a CharacterBlog about a crossover between the characters of Duel Monsters and the world of ''VideoGame/{{Persona 3}}''.
* Even though the first story of ''Fanfic/AStickySituation'' remains solidly in the ''[[Anime/DigimonTamers Digimon]]'' season three universe, the second story tosses several of the characters into ''WesternAnimation/StarWarsTheCloneWars'' due to a dimension-traveling digimon called Parallelmon (a {{Canon}} digimon, not an {{OC}} of the author). It is very well written and very entertaining.
* FanFic/{{Avalon}} is a bit of an odd example, being a cross between mainly ''{{Neon Genesis Evangelion}}'' and the ''Franchise/{{Marvel Cinematic Universe}}'' as the forefront, but with other Marvel properties also being mentioned as well as references to other fictional settings exsisting within the story. So far {{Rosario to Vampire}} and the Franchise/{{Stargateverse}} have explicitly been mentioned as part of the shared universe.
* [[http://www.fanfiction.net/s/8985296/1/Avengers-The-Next-Generation This crossover]] between ''Film/TheAvengers'' and ''Film/PitchPerfect''. It features Beca as Tony and Pepper's daughter and the rest of the cast as various superheroes.
* [[Film/TheAvengers Avengers]] crossed with [[Literature/TheHungerGames Hunger Games]] has some surprisingly good crossovers, including the [[AnyoneCanDie heartbreaking]] [[http://archiveofourown.org/works/413095/chapters/685873 Embrace the Fire]] and [[SparedByTheAdaptation less hearbreaking]] [[https://www.fanfiction.net/s/9775871/1/Something-to-Avenge Something To Avenge]].
* [[http://games.adultfanfiction.net/story.php?no=600086731 Bayonsiders]] has War from ''VideoGame/{{Darksiders}}'' and Bayonetta from ''VideoGame/{{Bayonetta}}'' meet up, have sex, beat up angels, beat up demons, and have sex while beating up angels and demons at the same time. All while trying to stay in continuity of both games.
* ''FanFic/BetweenMinds'' crosses {{Videogame/Portal}} and {{HalfLife}}.
* [[http://www.fanfiction.net/s/5493333/1/Brother_Bubbles Brother Bubbles]]. Space Marine Terminator finds himself in Rapture. Then meets a Little Sister.
* [[FanFic/BrutalSeries Brutal, Horrible, and What If]] is a series of crossovers between ''Manga/AxisPowersHetalia'' and the Hunger Games. Also AlternateUniverse.
* ''[[http://z4.invisionfree.com/Refia/index.php?showtopic=1010 Callisto Meets The Powerpuff Girls]]'' sends one of the [[BigBad Big Bad]] villains of ''Series/XenaWarriorPrincess'' to Townsville, and naturally WesternAnimation/ThePowerpuffGirls are called in to save the day.
* ''Fanfic/CalvinAndHobbesTheSeries'' has a crossover ''episode'' - "Calvin's Franchise/{{Batman}} Adventure".
* There are a few fics that cross over all the {{Nicktoons}}. One that does this along with extreme AU along with Alternate History (Vlad is now king of an FictionalCounterpart of America!) would be [[http://chesspiece.smackjeeves.com Chess Piece]] by NeoYi. It's filled with tons of continuity nods and has everything, from ''TheWildThornberrys'', ''WesternAnimation/InvaderZim'', and ''WesternAnimation/DoraTheExplorer'' to ''{{Doug}}'', ''WesternAnimation/AaahhRealMonsters'', ''CatDog'', and ''WesternAnimation/MyLifeAsATeenageRobot''. Seriously; it is also [[RuleOfCool awesome]].
* ''Fanfic/TheCriesOfHaruhiSuzumiya'' is a crossover between ''LightNovel/HaruhiSuzumiya'' and ''VisualNovel/HigurashiNoNakuKoroNi''.
* The game-idea series [[http://crossoverx.wikia.com/wiki/Crossover_X_Wiki Crossover X]] practically ''lives'' on this trope. It even uses the word "crossover" in its name.
* [[http://www.fanfiction.net/s/10020026/1/Delivered-From-Frollo Delivered From Frollo]] crosses ''The Hunchback of Notre Dame'' with ''Fantasia''.
* ''Fanfic/DemonOfJustice'' is older than FanFictionDotNet and crosses Anime/MobileSuitGundamWing with [[TheWarGods Oath of Swords]], a high fantasy series.
* [[http://www.fanfiction.net/s/5803383/1/Divine_Intervention Divine Intervention]] The [[TheBoondockSaints MacManus brothers]] meet the [[Series/{{Supernatural}} Winchester brothers.]] And it is COOL.
* A favourite for many seems to be ''Series/DoctorWho'', due to the remarkable ease with which the Doctor can be inserted in any story just by having the TARDIS land there. One of the most famous, TheManWithNoName, is a ''Series/{{Firefly}}'' / ''Doctor Who'' crossover, which some say should be officially added to {{Canon}}.
** Yet it VERY strangely lists one of the unofficial rules of the internet dealing with crossovers (specifically, [[VideoGame/{{Touhou}} rule ⑨]]
** There's also ''Fanfic/AHero'', a crossover with ''Anime/PuellaMagiMadokaMagica'' which subverts most ''Series/DoctorWho'' crossover formulas by instead inserting [[ScaryDogmaticAliens Dalek]] [[MadScientist Sec]] to fix the mess.
** Another crossover that's become increasingly popular is SuperWho, which combines ''Doctor Who'' with ''Series/{{Supernatural}}''.
*** Add one more show, ''Series/{{Sherlock}}'', to get SuperWhoLock, which has become quite popular on Tumblr.
** All it took was one scene where a pony had a David Tennant-like hairstyle and an hourglass on his quarter. The result is that under crossovers at FanFictionDotNet, ''Doctor Who'' is the most popular thing to cross into the world of ''WesternAnimation/MyLittlePonyFriendshipIsMagic'', beating out Franchise/SonicTheHedgehog.
** ''Fanfic/ChildrenOfTime'' crosses Ten's era with Literature/SherlockHolmes '''and''' ''WesternAnimation/SherlockHolmesInTheTwentySecondCentury''. Holmes and Watson take Martha Jones' place in Season 3 as Companions, with just a handful of episodes staying close to the original. The Eleventh Doctor is planned to make an appearance eventually...
* ''FanFic/DungeonKeeperAmi'' is an improbable mix of ''VideoGame/DungeonKeeper'' and ''Anime/SailorMoon''. And quite good.
* [[http://www.fanfiction.net/u/1263379/gabriel_blessing Gabriel Blessing]] is well known for his two ''VisualNovel/FateStayNight'' crossovers:
** ''Fanfic/TheHillOfSwords'', a ''LightNovel/ZeroNoTsukaima'' crossover wherein Louise summons Shirou as her familiar. This FanFic revived the whole concept of "Let's have Louise summon a different person than Saito !"
** ''Fanfic/InFlight'', a ''Manga/{{Sekirei}}'' crossover where Shirou discovers his NotQuiteDead mother, Takami Sahashi, and replaces Minato as the Ashikabi of the North.
* Fanfic wise, it's almost impossible to find a fandom that ''doesn't'' have a crossover with ''Literature/HarryPotter. ''
** There are crossovers of ''TheLandBeforeTime'' with ''Franchise/StarWars'', ''[[Literature/InheritanceCycle Eragon]]'', ''VideoGame/MegaMan,'' and, in one case, ''VideoGame/{{Halo}}.'' [[http://www.fanfiction.net/s/3007925/1/Star_Wars_The_Land_Before_Time_A_Jedis_Destiny Amazingly, many find that the Star Wars/Land Before time crossover in question is actually good.]]
*** [[http://www.fanfiction.net/s/4307557/1/Harry_Potter_and_the_Land_Before_Time Found the cross between Harry Potter and The Land Before Time!]]
*** "Voldemort has found a way to go back [[ArtisticLicensePaleontology thousands of years]], to the time of the great dinosaurs"? That's not a promising opening line. There's even a [[http://www.fanfiction.net/s/5426174/1/ Land Before Time megacrossover series on FanFiction.net.]] Too bad [[SturgeonsLaw it's about the same as 90% of all fanfics.]]
** There is a really good one between ''Literature/HarryPotter'' and ''VideoGame/FinalFantasyVIII'' that starts when Harry, age 5, is magically transported to the world of [[VideoGame/FinalFantasyVIII FF8]] and once there he becomes a fine Gunblade fighter and is somehow able to use [[VideoGame/FinalFantasyVIII FF8]] magic and do everything one can in the game... without using Guardian Forces. He later has to go back to his own world, where an evil Dumbledore lays in waiting... See [[http://www.fanfiction.net/s/3471134/1/ here for the prequel+ Philosopher's Stone]] arc, [[http://www.fanfiction.net/s/3531911/1/ here for the Chamber of Secrets]] arc and [[http://www.fanfiction.net/s/3580477/1/ here for the Prisoner of Azkaban]] arc. It's a pity that the third arc is not finished...
** There's a small collection of ComicStrip/CalvinAndHobbes[=/=]Literature/HarryPotter crossovers, all involving Calvin being a wizard. Luckily this corner of fan fiction seems to be untouched by SturgeonsLaw, although that may be because they're so small in number. [[http://www.fanfiction.net/Harry_Potter_and_Calvin_Hobbes_Crossovers/224/266/ Give em a look.]] [[http://www.fanfiction.net/s/6548722/1/Calvin_and_Hobbes_in_the_Wizarding_World This one is particularly good so far.]]
** Harry Potter in ''Film/ThePrincessBride''. Hermione dreams the people she knows into the plot of the movie, with herself in the role of the Grandson being read the book by Dumbledore. [[http://www.fanfiction.net/s/135041/1/Harry_Potter_and_the_Florinese_Dream No, really!]]
** One involved the plot of Pretty Little Liars being re-imagined in the Potter universe. Unlike most other crossovers, the characters of both series don't actually meet. [[http://www.fanfiction.net/s/6701410/1/Pretty_Little_Witches Here it is]]
** Since both Harry and Edward Elric are looking for the PhilosophersStone at some point, there's a lot of crossover fanfiction with ''Manga/FullmetalAlchemist''.
** Snakeskins is, without a doubt, one of the best fanfics in the whole crossover with AxisPowersHetalia fandom, in which the two universes are blended amazingly and England and Italy are still their immortal Nation-tan selves while they're at Hogwarts. It... sound's kinda confusing, but it's a lot simpler in context.
* Highlander. You can dump Duncan or Connor or any of the other Immortals in almost any historical period; or assume, for a series set today that this or that character is Immortal; or for series set in the future, assume that someone from a 20th/21st C. series was a Highlander and hadn't lost his/her head before then.
* FanFic/TheInfiniteLoops structure allows for almost any crossover and, in the background, is technically a MegaCrossover.
* In''[[http://www.fanfiction.net/s/8514012/2/Keena-the-Defendants-of-Constan-Magic-Academy Keena & the Defendants of Constan Magic Academy]]'', starting in chapter 8, the group go to an AlternateUniverse that features characters from the anime film Loups=Garous.
* ''Fanfic/KyonBigDamnHero'' manages to become a crossover between LightNovel/HaruhiSuzumiya and ''TvTropes'', with ''VisualNovel/HigurashiNoNakuKoroNi'' and bits of [[spoiler:''VideoGame/{{Half-Life}}'']] added in as well.
* 4 crossovers with ''WesternAnimation/LooneyTunes'' and ''WesternAnimation/WinxClub'' have been done by [[http://www.fanfiction.net/~looneywriter]] and [[http://www.fanfiction.net/~kidswbyungsta]]. Sure enough, keeping in with the Looney Tunes style of humor, as well as adding characters from ''WesternAnimation/{{Animaniacs}}'', ''WesternAnimation/TinyToonAdventures'', and ''WesternAnimation/PinkyAndTheBrain'' may have helped them in being loved by many on [[http://www.fanfiction.net/]]
* One of the most prevalent type of ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' fan fics and fan works in general. The most regular kinds are those such as ''FanFic/BetterLivingThroughScienceAndPonies'' (''VideoGame/{{Portal}}'') and ''WebAnimation/TurnaboutStorm'' (''VisualNovel/AceAttorney''), where another series' characters are transported to Equestria, sometimes [[FisherKingdom turning into ponies in the process]], and {{Fusion Fic}}s such as ''Fanfic/FalloutEquestria'' ([[VideoGame/{{Fallout}} guess]]) and ''Fanfic/FriendsOfASolarEmpire'' (''SinsOfASolarEmpire'').
* Originally, the intent was for ''Fanfic/MyLittleUnicorn'' to be completely separate from ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' , but eventually it became a crossover, and then was fully integrated into a ''Franchise/MyLittlePony'' story.
* It's easier to count the things that Naruto hasn't had crossovers with when it's had crossovers with ''ComicStrip/TheBoondocks'', ''VideoGame/DukeNukem'', ''WesternAnimation/AquaTeenHungerForce'', ''Film/MeanGirls'', ''Godzilla'', ''Franchise/FridayThe13th'' and probably the strangest with ''MarriedWithChildren''.
* In this fanfic [[http://www.fanfiction.net/s/7382184/1/Phineas-and-Ferb-Attack-from-other-Dimensions crossover]] sequel to ''Main/PhineasAndFerbTheMovieAcrossThe2ndDimension'' have the characters of Phineas and Ferb teaming up with characters from other franchises. such as ''WesternAnimation/MyLittlePonyFriendshipIsMagic'', ''WesternAnimation/SpongeBobSquarePants'', ''VideoGames/SonicTheHedgehog'' ''TheVerse/MarvelUniverse'' and among others. for stop Dr. Heinz Doofenshmirtz, Plankton and villians from other universes from taking over the multiverse
* [[http://www.fanfiction.net/s/7897742/1/Platinum-Angel This fic]], a crossover of ''Manga/{{Chobits}}'' with, of all things, ''Franchise/AssassinsCreed'' (trope page [[FanFic/PlatinumAngel here]]). Word from the author is that the eventual sequel will add ''Manga/MidoriNoHibi'' to the mix as well.
* Decent [[http://www.fanfiction.net/Pokemon_and_Digimon_Crossovers/80/257/ Pokemon/Digimon crossovers]] are not that common in fanfiction, but of late some interesting new submissions have popped up. SturgeonsLaw may be applicable due to grammar issues, but those with decent grammar tend to be alright.
* ''[[http://www.fanfiction.net/s/7843635/1/Portalborn Portalborn]]'' is actually inspired by the [[VideoGame/{{Portal2}} Portal 2 Mod]] for [[VideoGame/TheElderScrollsVSkyrim Skyrim.]] In starts off using the original elements of Fall of the Space Core after pitting [[{{Tsundere}} The]] [[BloodKnight Dragonborn]] with the weird and cooky [[CrazySurvivalist Doug Rattmann]]. It gets crazy, then evolves with a mysterious and adventurous plot.
* FanFic/QuinnInWonderland: [[Series/{{Glee}} Quinn Fabray]] falls DownTheRabbitHole and ends up in [[Literature/AliceInWonderland Wonderland]]
* The ''Manga/RanmaOneHalf'' fandom loves to create crossovers. There exists several archives devoted to them. Particularly common are crossovers with ''Franchise/SailorMoon'' which has a sub genre called the FukuFic that has more fan fics written for it than most anime has fan fics total.
* Raquaza Master's [[http://s1.zetaboards.com/PokeTown_2/index/ Pokemon Squad]] fanfics are supposed to combine the characters from Franchise/{{Pokemon}}, ''WesternAnimation/KaBlam!'', ''Series/BarneyAndFriends'' (Barney is going to be one of the main antagonists), ''WesternAnimation/DannyPhantom'', ''WesternAnimation/{{Animaniacs}}'', ''Series/SesameStreet'' (Elmo's going to be an upcoming villain), many video games, and much, much more.
* The fancomic ''Webcomic/{{Roommates}}'' by [[http://asherhyder.deviantart.com/ Ashe Rhyder]] and its spinoff ''Webcomic/GirlsNextDoor'' by [[http://pika-la-cynique.deviantart.com/ Pika la Cynique]] are this -- a crossover between ''Film/{{Labyrinth}}'', ''Theatre/ThePhantomOfTheOpera'', ''PiratesOfTheCaribbean'', ''Literature/LesMiserables'', and occasionally ''Literature/HarryPotter'' -- the many fandoms that appeared only once or twice are too numerous to count. Both by now run rather independently of each other, with a frequent ContinuityNod and ShoutOut to each other during their many, many storylines. And they are also awesome.
* [[RulesOfTheInternet Rule ⑨]]: If it exists, there is a crossover with ''VideoGame/{{Touhou}}''. [[FanficRecs/TouhouCrossover The series even has its own article.]]
* Due to their popularity, it's very easy to find on deviantArt crossovers involving ''LetsPlay/TheRunawayGuys'', mostly by [=ThatOneNPC=]. The guys have crossed over with such works as ''TheWizardOfOz'', ''Literature/AliceInWonderland'', ''VideoGame/{{Portal2}}'', ''VideoGame/{{Slender}}'', ''VideoGame/ProfessorLaytonVSAceAttorney'' and ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' ([[http://fav.me/d4vqwcn no really]]), to name a few.
** Each of the guys themselves has been subject to individual crossover fanart. For instance, [[http://fav.me/d4wius7 here]] is fanart crossing over LetsPlay/{{Chuggaaconroy}} with ProfessorLayton. (Chugga liked it, by the way.)
* [[http://www.fanfiction.net/community/Seanzilla115-s-Multi-crossover-stadium/86737/3/0/1/ Seanzilla115's Multi crossover stadium]], This Fanfiction community contains some of the greatist crossover stories by the greatist authors Fanfiction.Net has to offer.
* ''FanFic/ShinjiAndWarhammer40K'' is sort of an odd example. It is not a story where the universes meet, being more of a ForWantOfANail story about Shinji getting a large amount of TabletopGame/{{Warhammer 40000}} pieces and rulebooks as a child. His different (happier) childhood makes for a more dynamic protagonist and leads him to influence the rest of the cast into making things that fit the TabletopGame/{{Warhammer 40000}} ethos more than the original Evangelion series did. It's not the straightest example of a universe to universe CrossOver.
** A more straightfoward example of a mostly in-universe crossover for Evangelion/Warhammer would be ''FanFic/ThousandShinji''.
* Is there anyone Franchise/SonicTheHedgehog hasn't met yet? The blue hedgehog has had crossovers with [[http://www.fanfiction.net/Sonic_the_Hedgehog_and_Percy_Jackson_and_the_Olympians_Crossovers/253/2622/ Percy Jackson]], [[http://www.fanfiction.net/Sonic_the_Hedgehog_and_Godzilla_Crossovers/253/448/ Godzilla]], [[http://www.fanfiction.net/Transformers_Beast_Wars_and_Sonic_the_Hedgehog_Crossovers/65/253/ Transformers]], [[http://www.fanfiction.net/Sonic_the_Hedgehog_and_Halo_Crossovers/253/1342/ Halo]], [[http://www.fanfiction.net/Sonic_the_Hedgehog_and_iCarly_Crossovers/253/2898/ iCarly]], [[http://www.fanfiction.net/Sonic_the_Hedgehog_and_Gorillaz_Crossovers/253/2340/ Gorillaz]], [[http://www.fanfiction.net/Mighty_Ducks_and_Sonic_the_Hedgehog_Crossovers/243/253/ the Mighty Ducks]], [[FanFic/FuckTheJesusBeam Tengen Toppa Gurren Lagann]], [[https://www.fanfiction.net/Sonic-the-Hedgehog-and-Strawberry-Shortcake-series-Crossovers/253/4511/ Strawberry Shortcake]] and [[https://www.fanfiction.net/Sonic-the-Hedgehog-and-Tinkerbell-Crossovers/253/3713/ Tinkerbell]]. Are any of these even remotely connected?
** But [[http://www.fanfiction.net/Sonic_the_Hedgehog_and_Mario_Crossovers/253/347/ we all know who the big winner is...]]
** [[http://www.fanfiction.net/s/7891955/1/Sonic-Generations-Friendship-is-Timeless This]] fanfiction crosses over ''Franchise/SonicTheHedgehog'' with the cast of ''WesternAnimation/MyLittlePonyFriendshipIsMagic'', in a reimagining of the plot of SonicGenerations. It goes far beyond what the original game gives, showing the author did their research. For instance, Ponyville serves as the central [[NoPunIntended hub]], similar to the White Void in the game, the Death Egg Robot battle in the original is replaced with Nightmare Moon and in this fanfiction, Tails fights Metal Sonic instead of Sonic, possibly a reference to ''VideoGame/SonicTheHedgehog4''. The author has even adapted the updated canon of Friendship is Magic into the fanfic. However, how the author intends to implement alicorn Twilight is currently unknown.
* It's crazy just how many crossovers on FanFictionDotNet exist between ''Franchise/SonicTheHedgehog'' and ''Franchise/SuperMarioBros''. Sure, [[VideoGame/MarioAndSonicAtTheOlympicGames this may have become canon]] but authors were doing it way before then.
* {{Spider-Man}} has a slew of crossovers on FanFictionDotNet. [[http://www.fanfiction.net/s/5011834/1/Web_of_Shadow_Fallout This one]] crossed with the TeenageMutantNinjaTurtles, and [[http://www.fanfiction.net/s/3914495/1/A_Hospital_In_Jersey this one]] crossed with ''Series/{{House}}'' are quite good.
* ''StarWars'' and ''Franchise/StarTrek''. The rivalry between their fanbases and The UltimateShowdownOfUltimateDestiny makes it a bygone conclusion feature some, and for those to require at least one major battle between the United Federation of Planets and the Galactic Empire, but there are certain exceptions.
** Another good one is [[http://sfdebris.com/unity.asp Unity]] by notable contributor SFDebris. What is a wormhole was connected from the Delta Quadrant circa Voyager's fifth season to the Star Wars Universe circa early Return of The Jedi, (disrupting the Rebel Alliance's attempt to attack the second Death Star.) Involved every character from TNG forward moving well into the future and exploring all the potential interactions in detail.
** To complete the trifecta of renowned Star Wars vs. Star Trek fanfics, there's [[http://bbs.stardestroyer.net/viewtopic.php?t=404&highlight= StarCrossed]].
* ''FanFic/{{Survivability}}'': The ''Manga/{{Bleach}}'' universe with an original plot, starring characters from different KPop groups (DongBangShinKi, SHINee, Big Bang, SuperJunior, B2ST, +other solo singers and actors).
* [[http://www.fanfiction.net/s/6095074/1/Takamachi_Nanoha_of_2814 Takamachi Nanoha of 2814]] is a ''MagicalGirlLyricalNanoha'' Crossover with ''Comicbook/GreenLantern''. Then, it started to cross over with ''everything'' by chapter 3. Written by the almost infamous Shadow Crystal Mage, so you know it's good. [[FanFic/TakamachiNanohaOf2814 Now with its own page.]]
* [[http://www.fanfiction.net/s/7941617/1/To_Kill_A_Thief To Kill A Thief]]. ''KamikazeKaitouJeanne'' [[XMeetsY meets]] ''Manga/DeathNote''.
* At least 300 crossovers of ''WesternAnimation/TotalDramaIsland'' are available on fanfiction.net
** [[http://www.fanfiction.net/~supertrip One writer]] has written the aptly named "Total Crossover" series. They are currently working on ''3'' installments at the same time. [[spoiler: The scenes with JimmyNeutron border on RevengeFic.]]
* This [[http://www.fanfiction.net/s/7878969/1/The-Transformers-Marvel-Continuty fanfic]] is a shared universe for the Transformers and Marvel characters. as of 2013 an standalone Marvel and an official crossover story are yet to be written, but there plans to do so
* Likewise, you will be able to find crossovers between {{Twilight}} and just about anything
** Not many Crossover fics have managed to be as awesome as [[http://www.fanfiction.net/s/4821971/1/Edward_meets_Sherlock_Holmes Sherlock Holmes vs Edward Cullen.]]
* When ''Fanfic/WithStringsAttached'' was first conceived, it was supposed to be a [[Music/TheBeatles Beatles]]/''TabletopGame/DungeonsAndDragons'' crossover. Luckily, the author quickly matured out of that notion, and the story turned into something far more interesting and complex, though its {{RPG}} roots are quite evident still.
* The longtime crossover champion for TV shows is ''The Witness'' by Michele Martin, which managed to cross ''Series/ForeverKnight'', ''Series/{{Highlander}}'', ''Series/TheXFiles'', ''Series/QuantumLeap'', and the ''Series/{{Starman}}'' TV series. Believe it or not, the fic manages to keep all those balls in the air successfully, and even bring in cameos from a few other series, all while following a coherent plot and keeping the characters in-character!
* Literature/TheWTFJournal crosses over at least five fandoms.
* ''WebAnimation/ZanyToTheMax'' has an episode where the Warners (it's an ''WesternAnimation/{{Animaniacs}}'' fan series) enter the world of ''TheTimeMachine'' and try to help the Time Traveler find Weena as part of a contest. If they win, they will be able to [[ImTakingHerHomeWithMe take Weena home with them]]. [[spoiler: They don't win. WebAnimation/{{Homest|arRunner}}ripe [[AuthorAvatar Runner]] does instead.]] The episode is implied to turn into a MassiveMultiplayerCrossover by the end.
-->'''News Reporter''': We just got reports of [[WesternAnimation/ThePowerpuffGirls three super-powered sisters from the city of Townsville, Animenia]], in the Warner Bros. studio.\\
'''Yakko''': Super-powered sisters? Townsville, Animenia? [[BorrowedCatchPhrase Yes!]] Come, Warners. We must prepare for tomorrow.\\
'''Wakko''': Why, Yakko? What are we going to do tomorrow?\\
'''Yakko''': [[WesternAnimation/PinkyAndTheBrain The same thing we do every day, Wakko]]. Unfortunately, I have no idea what that is.\\
'''WesternAnimation/PinkyAndTheBrain''': They're zany, and they're the Warners, eight, eight, eight, eight, eight.
** There is a crossover episode in every season.
*** In fact, Season 3 consists of ''[[UpToEleven entirely]]'' crossover episodes!
* An author on FFnet has created this [[http://www.fanfiction.net/s/2322545/1/Halo_Republic_Commando]] a Star Wars and Halo crossover where the characters of Republic Commando (and some friends and enemies) meet Master Chief and company in the Halo universe. There is a sequel that takes place mostly in the Star Wars universe during the events of the Original Trilogy.
* Another author has crossed over MegasXLR with [[http://www.fanfiction.net/s/7777108/1/The_Golem_of_New_Jersey Harry Potter]], [[http://www.fanfiction.net/s/7734042/1/Megas_Five0 Lilo & Stitch]] and [[http://www.fanfiction.net/s/7929483/1/Perry_XLP Phineas & Ferb]], crossed over Phineas & Ferb with [[http://www.fanfiction.net/s/7712752/1/Seasonal_Sentai_Summerranger Super Sentai]] and [[http://www.fanfiction.net/s/7858523/1/The_Platypus_Rider Kamen Rider]], and then combined all the previous into a [[http://www.fanfiction.net/s/7998417/1/Megas_Final_Wars Mega Crossover]]
* In Anime fanfiction (and sometimes in other media), a quite common way to establish a plot, especially in PeggySue fics, is to have a wish be granted by [[Manga/AhMyGoddess Belldandy or her sisters]]. Whether this crossover is minor or major varies between fics.
* One author has even crossed over (at various times) Transformers with [[http://www.transformersfanfic.com/viewstory.php?sid=2439&chapter=1 Knight Rider]], The [[http://www.transformersfanfic.com/viewstory.php?sid=865&chapter=1 Real Ghostbusters]], Franchise/MastersOfTheUniverse, [[http://www.transformersfanfic.com/viewstory.php?sid=873&chapter=1 Sailor]] [[http://www.transformersfanfic.com/viewstory.php?sid=866&chapter=1 Moon]], [[http://shebakoby.deviantart.com/art/Jewel-Of-4-Sparks-32879715 Inuyasha]], and [[http://www.transformersfanfic.com/viewstory.php?sid=5021&chapter=1 Judge Judy]].
* There are a lot of fanarts involving [[Disney/TheJungleBook Kaa]] the Snake hypnotizing various victims. Google search "Kaa" and you'll see what the deal is.
* While not a FanFic, [[http://www.youtube.com/user/LogoAttitude this Youtube user]] makes videos which present "what if" situations dealing with [[VanityPlate television logos]], which also includes gems like [[http://www.youtube.com/watch?v=r6r3yR0PzCE "What if Steven Bochco collaborated with 4K!ds Entertainment?"]].
* [[https://www.fanfiction.net/s/3510991/1/One-Piece-A-Smash-Adventure One Piece: A Smash Adventure]] by [[https://www.fanfiction.net/u/794512/Specter24 Spectre24]] has Manga/OnePiece characters crossover with various Nintendo franchises related to VideoGame/SuperSmashBros
** Due to it's increased popularity, other users have attempted to make similar crossovers based off this. Most notable is [[https://www.fanfiction.net/u/447022/Game2002 Game2002]] who basically took the same concept, this time with Touhou characters. His [[https://www.fanfiction.net/s/5681268/1/Touhou-Journey-to-the-Smashing-Beyond crossover]] was also a huge hit among fans.
* Crossovers are huge in all fanworks, one of the two or three biggest reasons to create them.
* FanFic/MegamiNoHanabira is a crossover between the unrelentingly dark Franchise/ShinMegamiTensei and the {{WAFF}}-y GirlsLove {{Eroge}} Sono Hanabira Ni Kuchizuke Wo.
* FanFic/MutantStorm is a Franchise/HarryPotter[=/=]Franchise/XMen crossover where Jean Grey is Lily Potter's twin sister, and she decides to take Harry into her family after the events in Literature/HarryPotterAndTheOrderOfThePhoenix
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