One consequence of Easy Amnesia is that a character can be up and about, wandering around with all their faculties about them but with no clue who they actually are. If their arch-enemies find them in this state, they may decide to turn a liability into an asset, by convincing the character that they're really on the bad guys' side.
Thus, the rest of the protagonists find themselves having to not only fight against the amnesiac character, with all his abilities turned to the service of antagonism, but somehow rescue and Deprogram him. If the experience has a larger toll on a character's loyalties or sense of self, even after regaining their memory, it becomes Amnesiac Dissonance.
Used mostly by the kind of show that would use Easy Amnesia in the first place. By necessity this pretty much requires an Idiot Hero to make any kind of sense- one hopes that most people would at least try to figure out who they are before quickly agreeing to a plan that involves killing or seriously maiming a large number of people. This can be averted if the bad guy did a more thorough job of brainwashing than just saying "clearly I am your friend" and the amnesiac just took his word for it.
Then again, Amnesiacs Are Innocent.
- Death Note removed some very important memories through the use of Applied Phlebotinum, resulting in the evil main character working whole-heartedly for the side of good, trying to figure out the identity of a mass-murderer without knowing he himself was the culprit. Of course, he had a plan for getting his memories back from the beginning (as well as killing anyone in his way or convincing them of his innocence), because Light is amazing that way. Misa's memories were manipulated the same way, multiple times.
- As far as the original manga (and anime?) are concerned, Mamoru is dead when Queen Beryl infuses his corpse with evil in Sailor Moon. In the dub, however, they make it clear Darien's still alive as Beryl erases his memories and creates a powerful lackey.
- In Pokémon, the Team Rocket trio managed to finally capture Ash's Pikachu after seven seasons via this method...until Pikachu regained his memory and the Reset Button was pushed at the end of the episode.
- In the Excel Saga manga Excel gets amnesia and winds up living with Umi Rengaya and her family, including Professor Shiouji, who works for Kabapu, sort-of-arch-enemy of Excel's boss Il Palazzo. All the while, Excel is replaced by a fake Excel so neither Elgala nor Hyatt realize she's gone. In the anime, as well, during its one totally serious episode, Excel forgets who she is after getting shot by Il Palazzo, and winds up being saved by the Municipal Defense Force.
- Hyatt gets amnesia in the manga too, and ends up getting engaged to her neighbor Watanabe. Until Il Palazzo restores Hyatt's memories and she leaves with him.
- The Saber Marionette J manga inverts this when the Saber Dolls (the Big Bad's Terrible Trio of Bodyguard Babes, and the Psycho Rangers for the heroic harem of superpowered robot girls) get amnesia when struck by lightning, and fall in Love At First Sight with the male hero, Otaru, after he repairs them. Amnesiac Dissonance kicks in once their memories start coming back.
- Trisha Elric/Sloth and Scar's Brother's Wife/Lust in the first anime version of Fullmetal Alchemist which is caused by how human ressurection works. Lust wants to change back to a human, while Sloth is trying to replace the Elric Brothers with Wrath. Though Sloth does get her memories back as her son Ed kills her.
- Captain Neo Roanoke of Gundam Seed Destiny, a Manipulative Bastard, Evil Mentor, and dark take on the Team Dad and Big Brother Mentor tropes is eventually revealed to be Mu La Flaga of Gundam Seed with his own memory gone, and false ones implanted on top.
- In the Franco-Belgian comic Thorgal, when the titular hero is stripped of his memory by the gods, Kriss of Valnor convinces him that he is a pirate lord.
- The Amazing Spider-Man had Doctor Octopus attempting this with Spidey.
- Medusa, queen of the Inhuman sub-species, was given amnesia by her evil brother-in-law Maximus, and was found hiding in a cave by the criminal mastermind called the Wizard, who made her Susan Storm's counterpart in his Frightful Four.
- An issue of The Batman Adventures had Catwoman turn an amnesiac Batman into "Catman".
- Some Space Pirates did this to Legion of Super-Heroes's Ultra Boy once. When it actually came down to ighting, he didn't like it. He tried fighting on the other side; that was much more natural to him.
- Reverted in a Disney Big Bad Wolf comic; BBW has a nasty fall when chasing the Three Little Pigs, gets Easy Amnesia, and Practical Pig convinces him he is a pig and got hurt when chased by a wolf. Cue Zeke Wolf becoming horribly scared of his own son...
- A vengeful enemy managed to do this to Modesty Blaise once, in order to make her kill her sidekick. It almost worked.
- A variation: In Michael Kurland's Professor Moriarty novel The Empress of India, there is a gang leader in London with a Chinese name (but he doesn't look Chinese). Turns out he's Sherlock Holmes. See, he'd been posing as a Chinese gang leader as part of his investigation. After he got a bad knock on the head, he forgot his real identity, but remembered his alter ego, and thought that's who he was. Eventually another knock on the head restores his memory.
- In Ian Fleming's novels, James Bond suffered from this for a period—specifically, starting at the end of the last chapter of You Only Live Twice and ending at the beginning of the first chapter of The Man with the Golden Gun.
- This happens after Artemis's mind-wipe, although to be fair he just reverted to his self before he met the fairies, which was a criminal mastermind.
- Power Rangers Zeo: Tommy is given amnesia by Prince Gasket, then convinced that the other rangers are evil.
- Subverted in the Stargate SG-1 episode "Past and Present", in which the amnesiac is discovered to be the evil mad scientist responsible for infecting an entire planet with an amnesia virus. She cured herself of the amnesia, then tried to kill herself when her old, murderous personality conflicted with her new, peaceful one. Eventually, she is re-amnesiaed so she can live a peaceful life on the planet where these whacky adventures took place.
- Subverted again in another episode of Stargate SG-1 where a murderer used a device to erase his own memories of the murder. However, since he had been in love with the murder victim, he then helped solve the murder, and then had his memories erased again.
- In the episode "Ill Gotten Grains" of Good Eats, Alton Brown gets Easy Amnesia, but is still a brilliant cook. He's rescued by Francis Andersen (his "biggest fan" and a dangerously obsessed pastiche of Stephen King's Misery), who tells him his name is "Abe," and...
Francis: ...you're here to create wonderful wheat recipes for my store.
Alton: I am?
Francis: Yes, and...and you live here with me.
- There was an episode of Monk where Monk gets bonked on the head, and a woman unscrupulously convinces him that he's her husband. This doesn't stop Monk from attempting to solve the mystery of the week, although it causes his OCD to become significantly less serious.
- In an episode of MacGyver, the Villain of the Week takes advantage of MacGyver's amnesia to convince him that Peter Thornton is actually a terrorist to be apprehended, and even supplies him with a gun to do the job. Since Mac's memory has started to come back, though, and since he and Pete are such good friends, it doesn't take long for Pete to talk him out of it.
- In another Mac-Gets-Amnesia episode, the writers play around a bit. Since all the flashes of memory (played by clips from other episodes) he gets are of explosions or other violent acts with him in the middle, Mac almost convinces himself that's he's really a Criminal Amnesiac.
- Hercules: The Legendary Journeys has a variation; as a result of a misfiring favor from Fate, Iolaus loses all his memories of working with Hercules... which is a large enough chunk of his life that it takes him back to his days as a teenage gang member, and he promptly hooks up with that week's villains.
- On Miami Vice, Crockett got amnesia while working undercover and began behaving as his cover identity would.
- On The Dukes of Hazzard, Bo Duke got amnesia and Boss Hogg convinced Bo that he was Hogg's son.
- Narrowly averted in an episode of Star Trek: The Next Generation. The villains of the episode make sure that the Enterprise's "mission" involves complete radio silence to keep them from talking to anyone who's either not on the ship or not a spy. Ultimately, the crew become suspicious when they realize the ship's advanced weaponry can reduce their foe's military equipment to scrap within a few seconds- a foe they've supposedly been fighting for several decades.
- An amusing semi-subversion pops up on the 1990's Zorro series remake, when Harmless Villain Sgt. Mendoza is conked and convinced he's a seriously ruthless bandit leader, and it's up to Zorro to rescue him without getting captured...
- Happened once on Sci-Fi's The Invisible Man. Big Bad, Arnaud, puts on an American accent and convinces the amnesic hero, Darien Fawkes, that Arnaud is Fawkes' brother (while Fawkes' brother, in reality, was killed by Arnaud).
- You could say this happens to Olivia in the third season of Fringe. Olivia gets captured by Walternate and through some technical mambo-jumbo that has to do with serums and the blood-brain barrier, manages to give her all of Alternate-Olivia's memories, skills, and emotions convincing her she is from that reality fighting against her own reality.
- In Pretty Guardian Sailor Moon, Mercury has a spell casted on her by Kunzite, causing her to become Dark Mercury for a period of a few episodes, before The Power of Friendship (with the help of the Mystical Silver Crystal) brings her back in the end.
- A particularly gut-wrenching example happens on Chuck in the fifth season's final arc. As Sarah suffers amnesia as a result of a faulty Intersect, she's convinced by Nicholas Quinn that Chuck and his allies are evil, and is promptly ordered to kill Chuck.
- A key plot point in Knights of the Old Republic is that the player is actually Darth Revan, former master to the game's curreng Big Bad. The game drops suble hints and references. Interestingly the amnesia is done by the Jedi Council, the good guys of the setting. If you embrace The Dark Side, then it's inverted and Evil All Along, if you choose the Light Side ending, then it's Heel Face Turn via Becoming the Mask. Either way, it's an excellent Tomato in the Mirror Plot Twist worthy of Star Wars.
- In Mario and Luigi: Superstar Saga, this gets pulled on Bowser, who doesn't turn evil, obviously (since he already was), but gets recruited by a two-bit thief to become half of the game's Goldfish Poop Gang.
- This happens a few times in Planescape: Torment. The first time it happens you can get them to confess about it after you've already done what they asked.
- Variation in the third Sly Cooper game. After beating the final boss, Sly gets hit and has amnesia. The first person to come up is Carmelita, the police officer who's been after Sly, and learning that he has amnesia, convinces him that he was her partner. The variation comes when an epilogue scene reveals that Sly doesn't actually have amnesia, and is just faking it to get out of the thieving business, which also leaves the series open enough for a sequel.
- A unique example occurs in one episode of Jackie Chan Adventures where Valmont convinces the amnesiac Tohru that he was a criminal working for him. What makes this unusual is that, technically, Tohru did work for Valmont, before his Heel Face Turn.
- Kung Fu Panda: Legends of Awesomeness: Taotie discovers that the Furious Five have lost their memory after being exposed to Po'smemory erasing move. While Po and Master Shifu are away, Taotie took the opportunity to use this to his advantage by having them attack Master Shifu and Po upon their return. When the Furious Five regain their memory, they attacked Taotie causing him to get away.
- The Danger Mouse episode "Public Enemy Number One" had Baron Greenback convince an amnesiac Danger Mouse he was really a super-thief known as "The White Shadow".
- Chip 'n Dale Rescue Rangers had it happen to Dale, who joined the cat mafia.
- Semi-example: In Transformers: Beast Wars, the upright, chivalrous Silverbolt was initially on the evil Predacon side. He was a newborn "blank" mechanoid, who had a personality but no memories. He had no clue Megatron was really the bad guy, but he figured it out soon enough.
- An episode of the Donkey Kong Country cartoon had Donkey Kong getting amnesia. Both King K. Rool and Kaptain Skurvy convince him he's on their sides.
- Sissi temporarily convinces an amnesiac Ulrich in Code Lyoko episode "Amnesia" that he is her boyfriend and his teammates are his arch enemies. This fails partly because, even without his memories, Ulrich can't stand her....
- Snively did this to Sonic once in the SatAM cartoon of Sonic the Hedgehog.
- A year later, the Archie comic book would do this plot as well, except it wasn't Snively giving the shots. The cover art to the second half of the story is shown above.
- An episode of Aladdin had Princess Jasmine getting amnesia, and Harmless Villain Abis Mal convinces her that she's in fact his evil daughter, a desert bandit. She upgrades to a eyebrow-raising black costume (complete with whip) and helps Abis take over the country, but then betrays him and decides to promote herself to main villain after realizing he's an imbecile.
- Happened in Spider-Man: The Animated Series episode "Make a Wish".
- This is helped thanks to some video of Jameson bad mouthing him as usual.
- Simon Belmont in an episode of Captain N: The Game Master.
- One episode of Superfriends has Superman getting knocked out by a comet and landing on the King Arthur IN SPACE planet. When some local revolutionaries try to beat him up and fail miserably, they ask him to become their leader to Take Over the World. Superman quickly decides that this priority is way more interesting than figuring out who he is, and topples the government to pave way for the revolution's primary objective- raising taxes. Naturally, it falls to the other Superfriends to stop him.
- One episode of Batman the Brave And The Bold has Batman getting amnesia while in his "Matches Malone" gangster persona and believing he is an actual crime boss.
- One of the Captain Caveman and Son shorts on The Flintstone Kids had Captain Caveman get amnesia and assume that he was a villain because he was dressed as one (A domino mask). Interestingly, the entire criminal element of the city helps his son get him back to normal - Captain Caveman is such an effective thief that the city soon runs out of places that the other criminals can rob.
- Krypto the Superdog: One episode had Krypto lose his memory due to red kryptonite. The Junkyard Dogs, a gang of Harmless Villain stray dogs, try to take advantage of Krypto by convincing him he's part of their gang. However, Krypto's heroic sense of justice still remains and a rescue of the dog leader's girlfriend (who wished for Krypto to regain his memory) brings him back to his senses.
- In the season 1 finale of Transformers Prime, Optimus Prime sacrifices the Matrix of Leadership to stop Unicron, along with all of his memories as Optimus Prime. Megatron immediately takes advantage of this opportunity to welcome his old friend Orion Pax into the ranks of the Decepticons.
- An accidental case in The Powerpuff Girls episode, "Los Dos Mojos": Mojo Jojo knocks out Bubbles from behind. Before going completely out, Bubbles opens her eyes one last time to see her assailant gloating over her, causing her to believe she IS Mojo Jojo once he wakes up.