History Main / SixthRangerTraitor

* Crona from ''Manga/SoulEater'' is taken in after turning good, then is manipulated back to Medusa to be TheMole.\\
In the anime, [[spoiler:Crona decides to stop working for Medusa and leave the DWMA out of guilt. Maka catches him/her on the way out and convinces Crona to stay and be their ally for the rest of the show]].\\
In the manga, [[spoiler:Crona disappears just after being discovered, turning out to have been called back by Medusa to her lair. Eventually, Crona kills Medusa, but (as Medusa planned) thought so lowly of him/herself for it that Crona decides to become a Kishin as Medusa planned and cause TheEndOfTheWorldAsWeKnowIt. Maka manages to talk Crona back, but by that point Crona had done so much wrong Crona ended up being a BarrierMaiden for the rest of his/her immortal life as repentance, or until Maka manages to rescue him/her, depending on your personal interpretation.]]
* Played with in ''Anime/SwordArtOnline'': [[spoiler:After losing in a duel to Heathcliff, Kirito is forced to join the Knights of the Blood. After a costly boss raid with [=KoB=], Kirito realizes Heathcliff is actually Akihiko Kayaba, creator of SAO and the one responsible for trapping all the players in the game. His ruse exposed, Kayaba reveals that he was setting himself up to betray the [=KoB=] and set himself up as the game's FinalBoss]].

* ''Fanfic/ADiplomaticVisit'': The epilogue of the fourth story, ''The Diplomat's Life'', reveals that [[spoiler:Lady Aputsiaq is secretly working for the same being who was served by Subtle Dancer from [[Fanfic/EscapeFromTheMoon the Doa-verse]], and stole the Gem of Sacanas from where Twilight had it stored and turned it over to them. Twilight herself remains unaware of the thief's identity.]]

* ''Film/DogSoldiers'' - [[spoiler: Megan, who was a werewolf in secret from the start and believed the squad could somehow save her, betrays the soldiers after coming to the conclusion that either they weren't there to help her and that they'd kill her if they found out her secret, or that their chances of surviving the night were nil, or a combination of both]].

* In ''Film/TheFaculty'', [[spoiler:Marybeth is this in a meta sense. While the other five protagonists didn't know each other before the events of the movie, they ''are'' pretty obviously based on the group from ''Film/TheBreakfastClub'' ([[JerkJock Stan]]'s counterpart is Andy, [[AlphaBitch Delilah]]'s is Claire, [[HollywoodNerd Casey]]'s is Brian, [[{{Delinquents}} Zeke]]'s is Bender, and [[MisunderstoodLonerWithAHeartOfGold Stokely]]'s is Allison), leaving one to wonder where Marybeth fits in. The answer: she doesn't. She's the [[HiveQueen queen alien]] leading the {{Puppeteer Parasite}}s that are taking over the school]].

* Oddly enough, the reality show ''Dance Moms'' has an example of this, when [[spoiler:the newest mother to the group, Cathy, defects back to her own dance studio, then decides to directly compete against her erstwhile colleagues in an upcoming competition. She even specifically states that now she's seen the Abbey Lee company from the inside, so she can use their own methods against them, going so far as to steal one of the children's music. Like most Sixth Ranger Traitors, she fails spectacularly]].

** [[spoiler:The Republic Trooper story inverts the trope, casting the player character as the newest member but being the only one of their squad to remain loyal after everyone else defects to the Empire.]]
** [[spoiler:The Imperial Agent story plays this straight and has this happen twice over; the player character themselves serves as one for a team Republic spies, acting as a double-agent to get info - only for ''another'' member of the team to be a double-agent themselves, except that they serve a [[GreaterScopeVillain third group]] who is inflaming the war for their own ends.]]

* ''Webcomic/TheCrossoverlord'': [[spoiler:The Green Avenger was this. Justified, because she was brainwashed by Smiling Man]].

* After the [[Comicbook/TeenTitans New Teen Titans]] formed, their first new member was Terra, a cute teen girl with a sad backstory. One year later...well, there's a reason that Terra's grand finale is called ''Comicbook/TheJudasContract''. (However, the Titans didn't return to status quo; ''The Judas Contract'' also introduced Jericho, who became a long-standing member of the team.)

* ''Franchise/PowerRangers'':
** Zhane in ''Series/PowerRangersInSpace'' actually disguised himself as a "Sixth Psycho Ranger" in order to confuse ThePsychoRangers.
** To the point, despite the trope name, this really hasn't happened in ''Franchise/PowerRangers''. Sixth Rangers have started as antagonists and even villains, but it's always been due to mind control or the manipulation of the truth. The closest examples would be ''Series/PowerRangersNinjaSteel'', where Brady's brother Aiden [[spoiler: turns out to be ActuallyADoombot sent by TheStarscream]], and the ''[[ComicBook/MightyMorphinPowerRangersBoomStudios Mighty Morphin' Power Rangers]]'' comic which introduced an actual "Sixth Psycho Ranger" called Psycho Green who is later revealed in the Year Two Deluxe Edition to be [[spoiler:the former Sixth Ranger of the [[Series/ChikyuuSentaiFiveman Supersonic Rangers]] of [[Series/PowerRangersTimeForce Xybria]] who, after being benched too many times by his leader, lured the core FiveManBand into a trap and killed them all. An act of betrayal that won over the favor of Dark Specter]].
** Probably the closest to this happening occurs in ''Series/ChoudenshiBioman'' in a two part story where a man tries to join the team and fights beside them but he gets rejected when he turns out to not have any powers. The villains take advantage of him by tricking him into letting them turn him into an evil ranger the others have to defeat. Unlike future sixths rangers he does not keep his powers after he is freed.
* The ''Series/{{Torchwood}}'' episode "Adam" had the eponymous mind-altering alien acting as the team's most trusted member. [[DramaticIrony The viewers know he's the bad guy all along]].

* Oddly enough, the reality show ''Dance Moms'' has an example of this, when [[spoiler:the newest mother to the group, Cathy, defects back to her own dance studio, then decides to directly compete against her erstwhile colleagues in an upcoming competition. She even specifically states that now she's seen the Abbey Lee company from the inside, so she can use their own methods against them, going so far as to steal one of the children's music. Like most Sixth Ranger Traitors, she fails spectacularly]].

* [[spoiler: Zoey]] from ''Series/HowIMetYourMother'' became one of these, after she grew very close with the gang and even dated Ted. However when [[spoiler: Ted said "no" to preserving an old building called the Arcadian]], said person revealed to have [[spoiler: kept the recording she made of Ted praising the Arcadian]] despite having promised to get rid of it.

* Khunag of ''VideoGame/{{Albion}}'' joins the party as the sixth ranger. He has little role for awhile. Then at one point, the player must infiltrate the cult he once belonged to, and he's the only guide available. He 'guides' the player into declaring war on the cult, slaughtering their best warriors and eventually killing the leader, with whom he had a score to settle.
* In ''[[AlternateUniverse Another Day]]'', the bonus chapter of ''VideoGame/TheWorldEndsWithYou'', [[spoiler:Rhyme]], of all people [[note]]this is the insanity that is ''Another Day''[[/note]] pulls this on Neku...er, Shuto's [[FiveManBand team]] of Tin Pin Slammer-playing heroes.
* In ''[[VideoGame/BaldursGateII Baldur's Gate II: Shadows of Amn]]'', your starting party consists of entirely of characters from the first game... and Yoshimo. Guess who betrays you?
* Harle in ''VideoGame/ChronoCross'', twice, betraying Lynx for you because [[spoiler:you are Lynx]] and then betraying you for [[spoiler:the Dragons]] after you beat FATE.

* [[spoiler:Onef]] of ''VideoGame/TheBannerSaga''. Is recruited from [[spoiler:Frostvellr]], and fills out this role in the party. Invariably turns on the party later on, as [[{{Foreshadowing}} pointed out]] by their class title [[spoiler:"Backbiter"]]. Ends up killing a good number of your clansmen along with [[spoiler:Egil]], and [[spoiler:Oddleif]] comes scarily close to dying as well.
* ''VideoGame/UltimaV'' has [[SdrawkcabName Saduj]] who can join your party, but it turns out he's a spy for the BigBad, not just that but he'll flee every battle you enter massively dropping your karma eventually making the game unwinnable. Really the only use for him (Without him having to join) is that he's the only clue to the existence of the Sandalwood Box that is one of many items you need to beat the game, and that you can make him a [[UriahGambit Hairu]] in a particular battle.

* ''VideoGame/PhantasyStarIV'' has "Seth" who you meet at the entrance of a dungeon. [[spoiler:At the end of said dungeon, he turns out to be the third incarnation of Dark Force that you fight in the game.]]
* Penelope in ''VideoGame/Sly3HonorAmongThieves'' is technically the second recruit, and therefore the fifth ranger, but the way she joins is different from the Guru, Panda King, and Dimitri; they all join out of gratitude for the Cooper Gang's help with their own problems, while Penelope joined to keep her promise to Bentley. ''Nobody'' knew she had a [[AmbitionIsEvil very selfish motivation]] for joining until [[MoralEventHorizon it was too late]], and she betrayed the gang to Le Paradox in ''VideoGame/SlyCooperThievesInTime'' in order to harvest [[MealTicket Bentley's]] "potential" and TakeOverTheWorld.

* ''Film/{{Eternals}}'': The Eternals consider one another family. However, [[spoiler: Ikaris]] is so troubled by the group's plan to save Earth from [[PlanetDestroyer the birth of a Celestial]] that he kills [[spoiler: their leader, Ajak]], in hopes of replacing her, which would allow him to keep the information from the rest of the group and ensure all goes according to their orders. When that fails, he attempts to kill any member of the group who works against the Celestial's emergence. It proves a difficult fight as [[spoiler: Ikaris]] was their Second-In-Command and knows them quite well. He is also aided by [[spoiler: Sprite]] who has Loki-like powers of illusion and misdirection.

* The Swordsman, a VillainWithGoodPublicity, joined ComicBook/TheAvengers under orders from ComicBook/IronMan's enemy the Mandarin to sabotage the team. After gaining the trust of most of the team, he planted a bomb in their headquarters. It was after he had [[HeelFaceTurn a change of heart]] and disarms the bomb that he was found out and [[ReformedButRejected the team sent him packing]].

* After the [[Comicbook/TeenTitans New Teen Titans]] formed, their first new member was Terra, a cute teen girl with a sad backstory. One year later...well, there's a reason that Terra's grand finale is called ''Comicbook/TheJudasContract''. (However, the Titans didn't return to status quo; ''The Judas Contract'' also introduced Jericho, who became a long-standing member of the team.)

* ''Film/{{Eternals}}'': The Eternals consider one another family. However, [[spoiler: Ikaris]] is so troubled by the group's save Earth from [[PlanetDestroyer the birth of a Celestial]] that he kills [[spoiler: their leader, Ajak]], in hopes of replacing her, which would allow him to keep the information from the rest of the group and ensure all goes according to their instructions. When that fails, he attempts to kill any member of the group who works against the Celestial. It proves a difficult fight as [[spoiler: Ikaris]] was their Second-In-Command and knows them quite well. He is also aided by [[spoiler: Sprite]] who has Loki-like powers of illusion and misdirection.

* ''Film/DogSoldiers'' - [[spoiler: Megan, who was a werewolf in secret from the start and believed the squad could somehow save her, betrays the soldiers after coming to the conclusion that either they weren't there to help her and that they'd kill her if they found out her secret, or that their chances of surviving the night were nil, or a combination of both]].

* In ''Film/GraveEncounters2'' [[spoiler: Lance]] appears out of nowhere, having apparently survived [[spoiler: the first movie]] and shows up to aid the remaining survivors. Too bad for them he is taking orders from the hospital itself which speaks by scratching words into the walls or following him around invisible in the darkness of the hospital. To make this even worse, he [[spoiler: kills Trevor]] and attempts to escape the hospital himself. [[spoiler: too bad the demons of the hospital double crossed him too.]]
* ''Film/{{The Avengers|2012}}:'' Hawkeye, an archer, the sixth member of the Avengers, who had no speaking lines prior to this film, is mind-controlled by [[BigBad Loki]] and fights for him until the third act of the movie.
* In ''Film/TheFaculty'', [[spoiler:Marybeth is this in a meta sense. While the other five protagonists didn't know each other before the events of the movie, they ''are'' pretty obviously based on the group from ''Film/TheBreakfastClub'' ([[JerkJock Stan]]'s counterpart is Andy, [[AlphaBitch Delilah]]'s is Claire, [[HollywoodNerd Casey]]'s is Brian, [[{{Delinquents}} Zeke]]'s is Bender, and [[MisunderstoodLonerWithAHeartOfGold Stokely]]'s is Allison), leaving one to wonder where Marybeth fits in. The answer: she doesn't. She's the [[HiveQueen queen alien]] leading the {{Puppeteer Parasite}}s that are taking over the school]].
* In ''Film/Seven1979'', Mailei reveals herself to TheMole inside TheSyndicate: providing to information to Harris and the feds on their plans to take over Hawaii, and then sent to help the Seven to stop them. However, she later turns out to be a double agent, providing TheSyndicate with information about how much the feds know, and tries to kill Cowboy.

* ''VideoGame/MassEffect3'': [[spoiler: Maya Brooks]] in the "Citadel" DLC. She pretends to be a low level, bumbling but well-intentioned Staff Analyst, helping to uncover the assassin who is attempting to kill Shepard by providing the team with dossiers, information, and advice. In actuality, she is behind the attempt, intending to kill Shepard and replace him with a clone that will allow her to use Shepard's connections and reputation to push her Human Supremacist agenda on the galaxy.
%%* This is how [[spoiler: Bass]] was introduced in ''VideoGame/MegaMan7''.
%%* ''VideoGame/MegaManX4'' - [[spoiler:Double. Not that that is a MeaningfulName or anything]].
* ''[[VideoGame/{{Onmyoji}} Onmyōji]]'': [[spoiler: Yaobikuni, who suddenly turns on her friends and reveals her motives after being taken to [[BigBad Kuro Seimei]]'s place. [[Headscratchers/{{Onmyoji}} She is still a playable character after this revelation]]]].

[[folder:Western Animation]]
* Terra from ''WesternAnimation/TeenTitans''. Unlike in the comics, where Terra was EvilAllAlong, Terra started as an ally, rejected membership over a misunderstanding, and had become TheMole by the time she took it up. If it wasn't obvious enough that Terra as a Titan wasn't going to last long, the episode following her joining the team has her suspiciously absent save a very brief non-speaking cameo in the end, and the title of the next episode when she actually appears as a member of the team? [[SpoilerTitle "Betrayal"]].
* William from ''WesternAnimation/CodeLyoko'' joins the team in the second-to-last episode of the third season, even though he was already considered 7 episodes ago. Although he is not evil and never becomes evil, his inexperience and cockiness combined with some errors from the heroes themselves led to XANA taking him over in the following episode. The surprise factor was actually legitimate, because the build-up was so long.
* In ''WesternAnimation/GIJoeSigma6'', [[spoiler:Firefly]] ends up betraying the team to Cobra.
* [[spoiler: Longarm Prime]] from ''WesternAnimation/TransformersAnimated'' is introduced in a flashback as Bumblebee and Bulkhead's loyal classmate in boot camp, but the end of the episode reveals him to be Shockwave in disguise.

* In ''WesternAnimation/ThunderCats2011'', [[spoiler:Pumyra is actually a DeadAllAlong FemmeFatale who wants Lion-O dead for accidentally abandoning her to die in the rubble of Thundera]].
* In ''WesternAnimation/{{Robotix}},'' the Protectons eventually revive another of their [[SealedGoodInACan frozen comrades]] into a [[BrainUploading robot body,]] but unknown to them, Nemesis switched things so the body actually houses the mind of one of his minions, Venturak.

* In Creator/GrantMorrison's run on ''Comicbook/XMen'', where the core team starts out as a FiveManBand, Xorn [[spoiler:isn't just a traitor, he's ComicBook/{{Magneto}} in disguise]]! ([[TheRealRemingtonSteele For a while, anyhow.]]) Change and (perhaps futile) attempts to escape the status quo were major themes in this run. The first to join the ''original'' FiveManBand (not counting the Professor) from the sixties, Mimic, ''also'' betrayed the team.
** ''ComicBook/NewXMenAcademyX'' has an interesting case with this happening to both the New Mutants and their rival team at the same time. Both teams were five groups of friends short of one to make a full training squad. Icarus was added to the Hellions, whom he barely knew, because Julian convinced him to join, and Wither joined the New Mutants after he returned to school. Once the FBI tried to arrest Wither, the Hellions decided to bust him out and Icarus, realizing how horrible the consequences such act would have, contacted the New Mutants and both groups fought. Once Wither was cleared of all charges he realized who his real friends were and asked to be re-assigned to the Hellions, while Icarus jumped at the opportunity to take his spot on the New Mutants.
* Nemesis Kid of the Legion in ''Comicbook/LegionOfSuperHeroes''. He joined the Legion to spy on them for the evil Khund Empire (and later became a member of the Legion of Super-Villains).

* Shun-Day was this to the [[ComicBook/LesLegendaires Legendaries]], acting as TheMole to her creator [[EvilSorcerer Skroa]]. She however [[BecomingTheMask become the mask]] and ends up saving the other Legendaries from him. [[TheHero Danael]] agreed to let her go as a gratitude, but warned her that the next time they'd meet, it'd be as enemies.
** Later subverted during the Anathos Cycle when Tenebris, [[DaddysLittleVillain Darkhell's daughter]], joins the team. Her motivations for helping the heroes are selfish, she is known to love her father, and two of the Legendaries (namely Shimy and Gryf) were expecting her to betray them, to the point Shimy tried to [[MurderIsTheBestSolution murder]] her once it appeared she was of no more use. Ironically, it turned out she ''never'' betrayed the team, even when Anathos [[WeCanRuleTogether gave her the opportunity to join her]] [[CurbStompBattle after he single-handedly defeated the other heroes]]. After the Cycle, she has become a full-time member of the group.

* The Swordsman, a VillainWithGoodPublicity, joined ComicBook/TheAvengers under orders from ComicBook/IronMan's enemy the Mandarin to sabotage the team. After gaining the trust of most of the team, he planted a bomb in their headquarters. It was after he had [[HeelFaceTurn a change of heart]] and disarms the bomb that he was found out and [[ReformedButRejected the team sent him packing]].
* After the [[Comicbook/TeenTitans New Teen Titans]] formed, their first new member was Terra, a cute teen girl with a sad backstory. One year later...well, there's a reason that Terra's grand finale is called ''Comicbook/TheJudasContract''. (However, the Titans didn't return to status quo; ''The Judas Contract'' also introduced Jericho, who became a long-standing member of the team.)
* Titan's ''WesternAnimation/TransformersAnimated'' Comic had a new character called Afterburn, who is [[ParodySue one of the greatest Autobots to ever live, who cured a fatal infection and has recommendations from Ultra Magnus himself]]. [[spoiler: He's really a soulless drone created by Megatron, who faked his credentials.]]

* ''Manga/FushigiYuugi'''s Chiriko was really a Seiryu Seishi named Amiboshii.

* Team Trinity in ''Anime/MobileSuitGundam00'' season 1. [[spoiler: Anew Returner ([[ManchurianAgent unwillingly]])]] fills the role in season 2.

* In ''Fanfic/PersonalityConflicts'', this is Tommy's greatest fear. Also played straight with Drew and BadFuture Tasha, but subverted with Ryan.

* [[spoiler: Zeakros]] in ''Fanfic/AceCombatTheEquestrianWar''.

* ''Film/TheLosers'' - [[spoiler: Roque]].
* ''Film/TheExpendables'' - [[spoiler: Gunnar. [[EasilyForgiven They let it slide]] before the [[Film/TheExpendables2 sequel]]]].
* ''Film/SuckerPunch'': [[spoiler: Blondie]].
* ''Film/TransformersDarkOfTheMoon'': [[spoiler: Sentinel Prime]].
* ''Film/TheItalianJob2003'' - [[spoiler: Steve]].

* Lando Calrissian acts as this at in ''Film/TheEmpireStrikesBack'' but he quickly makes a HeelFaceTurn and becomes a regular SixthRanger.
* In ''Film/TheHungerGames'', [[spoiler:Peeta Mellark]] is this to the Career Tributes like the novels below.

* ''Literature/LorienLegacies'' has also got this trope, except it's a '''[[spoiler:[[{{Pun}} Fifth]]]]''' ranger traitor.
* ''Literature/{{Dragonlance}}'' - [[spoiler:Eben Shatterstone]].

* Franchise/StarWarsExpandedUniverse:
** [[spoiler:Jacen]], though it's fairly obvious before he actually becomes a Sith.
** Kyp in the ''Literature/JediAcademyTrilogy''.
** In the Coruscant Nights Trilogy, [[spoiler: Dejah Duare]].

* In ''Literature/TheHungerGames'', [[spoiler:Peeta Mellark]] is this to the Career Tributes.

* [[spoiler: Leek]] from ''Series/{{Primeval}}''. And Christine. And Philip. If the team (or Nick in series 2, and Abby in series 5) hate somebody, then that person is, guaranteed, to be evil!

* Jorge del Salto from ''Series/{{Carrusel}}''.

* Judas Iscariot, the UrExample.

* Mordred in the Myth/KingArthur [[Myth/ArthurianLegend mythology]].

* ''VideoGame/MassEffect3'' has [[spoiler: Maya Brooks]] in the "Citadel" DLC.
* This is how [[spoiler: Bass]] was introduced in ''VideoGame/MegaMan7''.
* ''VideoGame/MegaManX4'' - [[spoiler:Double. Not that that is a MeaningfulName or anything]].

* ''Film/XMenFirstClass'': [[spoiler: Angel]] abandoned the team after their CIA safehouse is attacked, not long after the newly formed team spent the evening demonstrating their abilities to one another. [[spoiler: Magneto and Raven]] decide it's dangerously naive to continue to work with the CIA-backed team after the combined US and Cuban militaries attempt to kill the Mutant squad that has just kept the two countries from initiating what promised to be a costly and destructive war. This attempted genocide and subsequent decision is after Charles has spent time helping [[spoiler: Magneto]] strengthen his already formidable but inconsistent abilities.

* ''Film/XMenFirstClass'': [[spoiler: Angel, Mystique and Magneto]].

->''"Already there used to be six of you and now there are just five. Pretty soon, Jake, it'll be four."''
-->-- ''Literature/{{Animorphs}}''

{{NOT}}

* In ''Anime/DigimonUniverseAppMonsters'', the Applidrivers gain a SixthRanger in the form of [[spoiler: Yuujin Oozora, Haru's best friend, and his Buddy Appmon Offmon]] mid-series. Rei finds the new addition to the team too eager to help and friendly, but the other Applidrivers and their Buddy Appmon see this as a bonus and welcome their new teammates with open arms. In the climax of the series, the horrible truth is revealed: [[spoiler: Yuujin is actually YJ-14, an ArtificialHuman created by [[BigBad Leviathan]] to [[DeepCoverAgent keep tabs on Haru and collect data on humans by living among them]]. Even his own Buddy Appmon didn't know this!]] This is obviously devastating to the Applidrivers, especially Haru. [[spoiler: However, being Haru's friend for half a decade made Yuujin grow a heart and personality of his own, so Leviathan has to take total control of his body to make him fight against his loved ones. When he regains control of his body, Yuujin is heartbroken about Leviathan's actions, and ends up making the choice to [[HeroicSacrifice delete Leviathan at the cost of his own life]], partially to prevent Haru from making that awful choice himself and living with that for the rest of his life.]]

* In ''Anime/DigimonUniverseAppMonsters'', the Applidrivers gain a SixthRanger in the form of [[spoiler: Yuujin Oozora, Haru's best friend, and his Buddy Appmon Offmon]] mid-series. Rei finds the new addition to the team too eager to help and friendly, but the other Applidrivers and their Buddy Appmon see this as a bonus and welcome their new teammates with open arms. In the climax of the series, the horrible truth is revealed: [[spoiler: Yuujin is actually YJ14, an ArtificialHuman created by [[BigBad Leviathan]] to [[DeepCoverAgent keep tabs on Haru and collect data on humans by living among them]]. Even his own Buddy Appmon didn't know this!]] This is obviously devastating to the Applidrivers, especially Haru. [[spoiler: However, being Haru's friend for half a decade made Yuujin grow a heart and personality of his own, so Leviathan has to take total control of his body to make him fight against his loved ones. When he regains control of his body, Yuujin is heartbroken about Leviathan's actions, and ends up making the choice to [[HeroicSacrifice delete Leviathan at the cost of his own life]], partially to prevent Haru from making that awful choice himself and living with that for the rest of his life.]]

* In ''Anime/DigimonUniverseAppMonsters'', the Applidrivers gain a SixthRanger in the form of [[spoiler: Yuujin Oozora, Haru's best friend, and his Buddy Appmon Offmon]] mid-series. Rei finds the new addition to the team too eager to help and friendly, but the other Applidrivers and their Buddy Appmon see this as a bonus and welcome their new teammates with over arms. In the climax of the series, the horrible truth is revealed: [[spoiler: Yuujin is actually YJ14, an ArtificialHuman created by [[BigBad Leviathan]] to [[DeepCoverAgent keep tabs on Haru and collect data on humans by living among them]]. Even his own Buddy Appmon didn't know this!]] This is obviously devastating to the Applidrivers, especially Haru. [[spoiler: However, being Haru's friend for half a decade made Yuujin grow a heart and personality of his own, so Leviathan has to take total control of his body to make him fight against his loved ones. When he regains control of his body, Yuujin is heartbroken about Leviathan's actions, and ends up making the choice to [[HeroicSacrifice delete Leviathan at the cost of his own life]], partially to prevent Haru from making that awful choice himself and living with that for the rest of his life.]]

* In ''Anime/DigimonUniverseAppMonsters'', the Applidrivers gain a SixthRanger in the form of [[spoiler: Yuujin Oozora, Haru's best friend, and his Buddy Appmon Offmon]] mid-series. Rei finds the new addition to the team too eager to help and friendly, but the other Applidrivers and their Buddy Appmon see this as a bonus and welcome their new teammates with over arms. In the climax of the series, the horrible truth is revealed: [[spoiler: Yuujin is actually YJ14, an ArtificialHuman created by [[BigBad Leviathan]] to [[DeepCoverAgent keep tabs on Haru and collect data on humans by living among them]]. Even his own Buddy Appmon didn't know this!]] This is obviously devastating to the Applidrivers, especially Haru. [[spoilers: However, being Haru's friend for half a decade made Yuujin grow a heart and personality of his own, so Leviathan has to take total control of his body to make him fight against his loved ones. When he regains control of his body, Yuujin is heartbroken about Leviathan's actions, and ends up making the choice to [[HeroicSacrifice delete Leviathan at the cost of his own life]], partially to prevent Haru from making that awful choice himself and living with that for the rest of his life.]]

* Kaworu from ''Anime/NeonGenesisEvangelion'', although there's enough visual and in-plots hints about people wondering about him that he was deliberately a mysterious character. His character showed up in one episode, which means the time from Introduction to TheReveal about [[spoiler:his identity as The Last Angel]] was about ''fifteen minutes''. Subsequent versions of the story reveal it even faster, likely because [[ItWasHisSled almost anyone watching a remake will know it anyway]]. ''Death & Rebirth'' reveals Kaworu's betrayal before introducing him! The fact that he's first seen in ''Anime/RebuildOfEvangelion'' hanging out with Keel Lorenz is a pretty big indication by itself that he's not on NERV's side in the latest iteration of the story, either. [[note]]there is subversion in that He's not with SEELE or even the Angels, either in the end. He picks to side with the Lilim, and decides to at least buy some time for Shinji to survive. Not much good that did anyway, but it's the thought that counted.[[/note]]
** There's also EVA-03 and its pilot, however the case of their betrayal was unintentional, as an Angel managed to hijack them before they even made a sortie.

* In the second season opening of ''Anime/ScienceNinjaTeamGatchaman'', the team gets a new G-2 as a replacement for dead [[TheLancer Lancer]] "Condor Joe" Asakura, much to the others' discomfiture. Surprise! He's a Galactor agent. Double surprise! [[spoiler: Joe, BackFromTheDead, kills him.]]

* ''Manga/FushigiYuugi'''s Chiriko was really a Seiryu Seishi named Amiboshii.

* [[spoiler:Meowth of Team Rocket]] pretends to become a new ally for the heroes of ''Anime/{{Pokemon}} Best Wishes'' for one short StoryArc, but it was just to lure them into a trap in Nimbasa City.

* In ''Manga/AttackOnTitan'', Floch Forester is a late arrival to the cast, having been a classmate of the main characters that did not enlist in the Survey Corps. He has a change of heart and decides to switch branches to begin working with his old classmates and ''seems'' to be a RedShirt in the making. Instead, [[spoiler: he's the SoleSurvivor of the suicide charge against the Beast Titan]]. After the TimeSkip, he quickly establishes himself as a TokenEvilTeammate that clashes with Jean over [[WouldHurtAChild ethics]] and eventually betrays the Survey Corps entirely as TheDragon to [[spoiler: Eren's radical Yeager Faction]].

* ''Literature/{{Animorphs}}'' - [[spoiler:David]]. Note that no one really wanted him to join, and he didn't either, but [[spoiler:he'd found the morphing cube and his parents had been taken by Yeerks.]] He ends up [[spoiler:permanently trapped in rat morph]], and his fate [[spoiler:(MercyKilled by Rachel or left to live as a rat)]] is left deliberately vague.

* Discord pulls this stunt in the Season 4 Finale of ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' after listening to Tirek's HannibalLecture. Getting swiftly backstabbed, [[ManaDrain drained of his powers]], and ''still'' forgiven by his former friends kicks him back to the pony's side for good... [[HeelFaceRevolvingDoor probably...]] [[ReformedButNotTamed hopefully]].
** WordOfGod is that all groups of 6 heroes have one of these. The [[PrecursorHero Pillars of Old Equestria]] has Stygian, the Mane 6 have Starlight Glimmer (and debatably Sunset Shimmer as well), and the Young 6 have Cozy Glow. The first two performed a HeelFaceTurn, while Cozy Glow... [[EnfantTerrible didn't.]]

* Nemesis Kid of the Legion in ''Comicbook/{{Legion Of Super-Heroes}}''. He joined the Legion to spy on them for the evil Khund Empire (and later became a member of the Legion of Super-Villains).

** Probably the closest to this happening occurs in ''Series/ChoudenshiBioman'' in a two part story where a man tries to join the team and fights besides them but he gets rejected when he turns out to not have any powers. The villains take advantage of him by tricking him into letting them turn him into an evil ranger the others have to defeat. Unlike future sixths rangers he does not keep his powers after he is freed.

** Probably the closest to this happening occurs in ''Series/ChoudenshiBioman'' in a two part story where a man tries to join the team and fights besides them but he gets rejected when he turns out to not have any powers. The villains take advantage of him by tricking him into letting them turn him into an evil ranger the others have to defeat.

* ''Literature/VillainsByNecessity'': Robin.

** In ''VideoGame/FinalFantasyIV'', when returning to Baron, you run into Cecil's old friend Chancellor Baigan. He "joins" your party (despite the fact that your party is already full; the game doesn't ''allow'' six playable characters to be used at once) and he follows along behind you unlike all the other party members who aren't shown on screen during normal gameplay). He is revealed as a monster in disguise about five seconds later. In the DS remake, this is played as a cutscene and Baigan has a new 3D model, and he immediately reveals himself as a monster in the cutscene.

* ''Film/{{The Avengers|2012}}:'' Hawkeye, an archer, the sixth member of the Avengers, and the one who had just been introduced in this film, is mind-controlled by [[BigBad Loki]] and fights for him until the third act of the movie.

** Topher is introduced as a kid apparently in a similar position to the heroes, and is a little too charming and eager to get on with everyone. He turns out to be a vampire and tries to murder them all. His betrayal causes the team to be initially suspicious of SixthRanger ComicBook/VictorMancha, especially since they know he's [[LukeIAmYourFather the son of a villain]] (though they don't know which one for a while) and supposedly destined to [[FaceHeelTurn turn evil]]. Given that every single fricken one of them is the child of at least one, and in most cases two villains, what do ya expect?

** To the point, despite the trope name, this really hasn't happened in ''Franchise/PowerRangers''. Sixth Rangers have started as antagonists and even villains, but it's always been due to mind control or the manipulation of the truth. The closest examples would be ''Series/PowerRangersNinjaSteel'', where Brady's brother Aiden [[spoiler: turns out to be ActuallyADoombot sent by TheStarscream]], and the ''ComicBook/MightyMorphinPowerRangersBoomStudios'' comic which introduced an actual "Sixth Psycho Ranger" called Psycho Green who is later revealed in the Year Two Deluxe Edition to be [[spoiler:the former Sixth Ranger of the [[Series/ChikyuuSentaiFiveman Supersonic Rangers]] of [[Series/PowerRangersTimeForce Xybria]] who, after being benched too many times by his leader, lured the core FiveManBand into a trap and killed them all. An act of betrayal that won over the favor of Dark Specter]].

** To the point, despite the trope name, this really hasn't happened in ''Franchise/PowerRangers''. Sixth Rangers have started as antagonists and even villains, but it's always been due to mind control or the manipulation of the truth. The closest examples would be ''Series/PowerRangersNinjaSteel'', where Brady's brother Aiden [[spoiler: turns out to be ActuallyADoombot sent by TheStarscream]], and the ''ComicBook/Mighty MorphinPowerRangersBoomStudios'' comic which introduced an actual "Sixth Psycho Ranger" called Psycho Green who is later revealed in the Year Two Deluxe Edition to be [[spoiler:the former Sixth Ranger of the [[Series/ChikyuuSentaiFiveman Supersonic Rangers]] of [[Series/PowerRangersTimeForce Xybria]] who, after being benched too many times by his leader, lured the core FiveManBand into a trap and killed them all. An act of betrayal that won over the favor of Dark Specter]].