The Turncoat is the guy who switches sides at some point to help out the other side. Can be a hero who turns bad, or a bad guy who suddenly decides to help the good guys, but usually it's just anyone who thinks that the switch will benefit them personally.
If they're discovered to have been bad the whole time, they're The Mole. If they're a bad guy who's been secretly good, they're the Reverse Mole. If they're faking their switch, they're a Fake Defector or Heel–Face Mole. If they switch back and forth, they're going through the Heel–Face Revolving Door.
There are several possible motivations. Someone who decides that their side is corrupt or otherwise unworthy may become a Defector from Decadence; someone who simply wants to end up on the winning team may decide that I Fight for the Strongest Side.
It's interesting to note the origins of the phrase "turn coat". Back in the day (we're talking horse and musket age) soldiers defecting to the other side would turn their coats around so the liner would face the outside, to indicate they were not a soldier of the enemy. Of course, one only did this when you were far enough away from your own lines...
- Beyblade: Kai Hiwatari switches sides six times. First, he's part of the antagonistic Blade Sharks. Then he joins the Bladebreakers (first switch). Then he switches sides and joins the Demolition Boys (a Face–Heel Turn, and switch #2). Then he switches sides again and rejoins the Bladebreakers (three). He stays with them until he goes over to the Blitzkrieg Boys (the Demolition Boys renamed, and switch number four). His next move is to join the bad guys of season three, BEGA (five). Of course, he realizes the error of his ways and switches back again (six).
- Uryuu Ishida goes from being an enemy of Ichigo and the shinigami to an ally... albeit with loopholes helping him along the way to protect his pride.
- Aizen, Gin and Tousen betray Soul Society to join Hueco Mundo. Then Aizen betrays Hueco Mundo and Tousen. Aizen and Gin betray each other.
- In the Zanpakutou Arc, Byakuya betrays the shinigami to side with the rebelling zanpakutou. He's actually a Fake Defector.
- Flarejet in Transformers: Operation Combination, a Decepticon who used to be an Autobot and a friend of Firefoad
- Justin Law in Soul Eater defects from the DWMA to become a devotee to the Kishin.
- The Legend of Zelda: Four Swords: Vio (Fake Defector) and Shadow (Heel–Face Turn).
- InuYasha: Kagura desired her freedom from her enslavement to Naraku. As the story develops, she helps Sesshoumaru against Naraku more and more and begins to aid Inuyasha's group against him, too. When she takes active measures to save Kohaku's life, Naraku finally ends hers.
- In All Fall Down, Pronto becomes this in exchange for a new pair of legs.
- The 4th Touhou M-1 Grand Prix had Utsuho, Orin, Satori & Koishi swap partners.
- Cypher, in The Matrix.
- Little Giants: Spike Hammersmith when he leaves the Little Giants and plays for the Cowboys after initially joining the Giants because Danny fibbed and said he was Kevin. Considering how he was tricked into joining the Little Giants in the first place, can anyone really hold it against Spike?
- Richard Cameron from Dead Poets Society, who is worried about getting caught in the Society's off-campus secret parties, and informs Dean Nolan of the Society's activities after Neil's suicide, resulting in Keating's forced resignation from the Welton teaching staff.
- A Song of Ice and Fire is filled with these. Particularly sellswords, who will abandon battle and even turn against those who hired them and join the enemy if the tide is against them.
- Theon Greyjoy is dubbed Theon Turncloak by the Northeners after he rejoins his family and betrays Robb.
- On Robb's side is also Lord Roose Bolton and Lord Walder Frey. They betray the Starks at the Red Wedding, when in a shocking violation of guest right the Freys kill his mother and most of his army, Roose personally murdering Robb.
- Because rule of the Stormlands is contested early on by three different members of House Baratheon, it becomes something of a Running Gag for any given Stormlord to rapidly change sides due to changing circumstances. Given the cynicism of the series, those that do not switch sides end up suffering for not being able to adapt.
- The Second Sons once sworn themselves to Daenerys, then they switched sides with Yunkai when they lay siege to Meereen. Then its revealed they were playing Fake Defector, and were really on Daenerys side all along.
- "The Princess and the Queen", an in-universe history about a civil war between two branches of the Targaryen dynasty (the Greens and the Blacks), has Hugh Hammer and Ulf the White. They are dragonseeds (illegitimate descendants of those with Valyrian blood), who are recruited to become dragonriders by the Black claimant, Rhaenyra. However they betray her army at Tumbleton, joining the Greens for unknown reasons. Later they prove treacherous to the Greens, planning to seize power themselves. This leads to the Greens murdering them.
- Harry Potter: Peter Pettigrew, who sold out two of his best friends, Lily and James Potter, to Voldemort, and then framed a third friend, Sirius Black, for the whole thing. He considered turning back (just a little bit!) after Harry Potter saved his life, but the mere thought of betraying Voldemort caused his magical prosthetic arm to strangle him.
- Esmer in The Last Chronicles of Thomas Covenant is chronically unable to choose a side, to the annoyance of everyone involved. He has the rare distinction of being able to switch sides several times a day and the personal power to pull it off.
- Warhammer 40,000: In Ben Counter's Horus Heresy novel Galaxy In Flames, Lucius motivated by envy of how Tarvitz took command, betrays the last survivors of Horus's treacherous attack.
- In Edgar Rice Burroughs's Chessmen of Mars, the ancient I-Gos is perpetually praising his days. So thorough is his admiration that he changes his loyalties on realizing who is The Hero.
Then I did not fully realize the cowardice of my jeddak, or the bravery of you and the girl. I am an old man from another age and I love courage. At first I resented the girl's attack upon me, but later I came to see the bravery of it and it won my admiration, as have all her acts. She feared not O-tar, she feared not me, she feared not all the warriors of Manator. And you! Blood of a million sires! how you fight! I am sorry that I exposed you at The Fields of Jetan. I am sorry that I dragged the girl Tara back to O-Tar. I would make amends. I would be your friend. Here is my sword at your feet.
- In Discworld, Nobby Nobbs is famous in times of war for exactly this. He hovers around the edge of the battlefield, swiping boots off the fallen soldiers and will just move in with whoever he thinks is winning. The generals used his uniform as an indicator to tell who was winning.
- In Mercedes Lackey's The Black Gryphon, two of Urtho's generals seem to be carrying the Idiot Ball for most of the book; they're constantly losing troops of all species by attempting flashy, dangerous tactics which would lead to glorious victories, if only they actually worked; it later comes to light that these losses are intentional, as they have been working for the enemy for some time.
- Conan the Barbarian:
- In Rogues in the House, Conan's Back Story includes being betrayed by a woman. After he's out of prison, he tracks her down and (since she is a woman) abducts her to drop her in a cesspit.
- In The Hour of the Dragon, Publio turns on Conan because Conan's presence might reveal that his wealth springs from dealing with Conan when he was a corsair.
- In "The Scarlet Citadel" Amalrus, who lured Conan into an inverted Cavalry Betrayal.
- Happens in John le Carré, along with moles, with regularity, since that's the whole point of having agents and double agents. As one character put it:
Don't feel too bad. Christ himself only had twelve, and one of them was turned.
- In Harald, the leader of King James's secret police betrays him when James makes a Heel–Face Turn.
- Not that Kallor made the most trustworthy impression beforehand, but his betrayal still comes as a bit of a shock to his superiors in Malazan Book of the Fallen. Nobody thought that he would willingly join the Crippled God just to get a shot at Silverfox.
- Buffy the Vampire Slayer: Faith (Face-Heel, then Heel-Face) and Spike (Heel-Face, then Face-Heel, then back Heel-Face). Not to mention Angel (Heel-Face when he got a soul, Face-Heel when he lost it, etc. ad nauseum). Also Andrew (Heel-Face) and Anya (Heel-Face, brief Face-Heel, then back to Heel-Face).
- AD Walter Skinner in The X-Files. He started a bit shady and it looked like he was working with the Cancer Man. He turned out to be one of the few good guys at the FBI and trusted ally for Mulder and Scully. Episode "S.R. 819" paints him as a turncoat who seeks benefits for himself. He has a touching scene in hospital where he tells Scully he wishes to be helpful. Yet at the end of the episode, he refuses to support Mulder and Scully's quest.
Skinner: I always played it safe. I wouldn't take sides. Wouldn't let you and Mulder... pull me in.
Scully: You've been our ally more times than I can say.
Skinner: Not the kind of ally that I could have been.
[several scenes later]
Skinner: So you still think this is about you? About the X-Files?
Mulder: Yes. Yes, I do. And I have an idea who may be behind all this. But I'd need your authority to continue the investigation.
Skinner: I have neither the authority nor the will to allow your continued inquiry into this matter. You'll perform your duties as directed by AD Kersh and only AD Kersh.
[Mulder and Scully stare at Skinner in surprise]
Skinner: This matter's closed, Agents. Am I clear?
- Juliet turned good while Michael turned bad and then good again.
- Ben often is in a Heel–Face Revolving Door, depending on who's side he's on at that moment and what his present goal is. He undergoes a final Heel–Face Turn in the final episode, after Hurley offers him a second chance at redepemption, as his Number Two while he settles into the role as new protector of the Island.
- In the final episode of Star Trek: Deep Space Nine, the Cardassian ships turn on their Dominion allies and aid the Federation Alliance fleet. Though the fact that one of their major cities on their homeworld had been wiped from the face of the planet might have had something to do with it. Gul Dukat fits this trope alone, when he realizes that the military is going to be overthrown he switches to back the civilians ("Way of the Warrior")
- Castiel of Supernatural is a Turn Coat to Heaven when he rebels. Ironically, this puts him on the side of good because the angels want to bring on the apocalypse.
- Final Fantasy II: Count Borghen betrayed Fynn to the Empire, becoming a general and leading to the assault that starts off the game.
- Final Fantasy IV: Kain Highwind switches sides four times throughout the course of the game. He was under More Than Mind Control from about one hour into the game to about one hour until the end of the game. Golbez just liked to screw with the heroes by slackening his control on Kain.
- Final Fantasy VII: Reeve Tuesti, controlling Cait Sith is The Mole for the bad guys at first, but quickly swaps sides wholeheartedly once he's found out, even taking a risk for the party through sacrificing one of his puppets for their cause.
- Tales of Symphonia: Yuan switches from allying with the heroes to trying to kill them so often even the other characters comment on how hard it is to keep track. It makes sense, as he's a double agent within the villains' organization, and leads his own organization opposing the villains that is easily confused with said villains. So he never really switches sides, just motives. Pretty much half of the cast betrays Lloyd at one point or another. Which makes you wonder just how naive he is.
- Played for laugh in Hyperdimension Neptunia Victory. When Nepgear is tricked to switch side to Vert, a notification told everyone that "Nepgear gained Turncoat affinity!"
- Zevran from Dragon Age: Origins may join your party after you foil his attempt to assassinate you for Loghain. If he does, depending on his Relationship Values, he might later turn around and rejoin the enemy.
- Fire Emblem
- Many recruitable characters start out on the enemy side, but can either be persuaded to join by your Lord character persuading them that their cause is wrong, your Lord character giving them a fat sack of cash, or a friend/relative/lover asking them to switch sides. Some examples include Beowulf from Fire Emblem Jugdral, who will turn against his employers if someone carrying 10,000 gold talks to him, and Tharja from Fire Emblem Awakening, a Plegian Dark Mage who finds herself disillusioned with her home nation and can join up with the Shepherds if Chrom talks to her.
- Treason in the heroes' home country or allies is also common. Binding Blade is particularly rife with this. Several lords in the so-called Lycian League throw in with Bern when it invades. A huge chunk of Ostia's army also betrays their land after Marquess Hector is killed and plot to kill his daughter Lilina. (They fail.)
- In Shōgi, captured pieces change sides.
- In Avatar: The Last Airbender, Azula joins forces with the imprisoned Long Feng and takes control of his Dai Li agents to capture the Avatar, overthrow the king, and free Long Feng from prison. Once the Earth Kingdom is under their control, Long Feng wants to dump her and rule by himself. However, during the time of her leadership, the Dai Li have come to greatly appreciate the ability and ruthlessness of Azula, so they just ignore his order to capture her, waiting for them to prove who is more worthy of their loyalty. Azula wins, easily.
- This happens a few times in Star Wars: The Clone Wars.
- Faro Argyus in Season 1 episode "Cloak of Darkness". He secretly works under Asajj Ventress to free Nute Gunray from Jedi custody.
- Clonetrooper Slick in Season 1 episode "The Hidden Enemy". It's revealed Slick was tired of being a 'slave' to the Jedi and decides to join forces with the Separatists.
- Pong Krell in the Umbara arc of Season 4, who leads the 501st in the Battle of Umbara. Turns out he was turning armies of clones against each other.
- Terra from Teen Titans manages to be both this and the mole. She starts off on the Titans side but is swayed over to Slade at the promise of him helping her control her powers, she then comes back and joins the team as The Mole.
- Xiaolin Showdown: Raimundo once betrayed his friends and joined Wuya. He later returned to them. Omi would later join Chase Young but that was justified by a Wu's effect. Raimundo also joined forces with Hannibal Roy Bean but in that case, he was just a Fake Defector.
- Jackie Chan Adventures: Tohru's Heel–Face Turn at the end of Season 1.
- Iago in Aladdin: The Return of Jafar, which gets a Lampshade Hanging in House of Mouse where Depending on the Writer, Iago is either Jafar's henchman or Aladdin's sidekick.