A close relative of EvilTwin and FreakyFriday, NotHimself is any plot where a character acts contrary to the way they normally behave. Can be used to provide a mystery to be solved, or to incite bewilderment in the other characters. The deviation is often a marked increase in [[DemonicPossession evil]], insanity, and/or horniness: the emergence of the [[ShadowArchetype inner shadow]] -- Or a [[SpotTheImpostor switcheroo]].

Sometimes, it's a detective or police character behaving as if they were corrupt, or a criminal. This will usually turn out to be the FakeDefector.

If the change is deliberate to save their friends, it's SomethingTheyWouldNeverSay.

Contrast with AsYouWish.
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!!Examples

[[foldercontrol]]

[[folder: Anime ]]

* Usagi and Mamoru in ''SailorMoon'' most likely because the other is involved in some way.
* Mimi in ''PerfectBlue'' throughout the majority of the movie. Also, Rumi towards the end.
* Lelouch on occasion in ''CodeGeass''. As well as Suzaku and Rolo once he starts to become closer to Lelouch.
* ''{{Utena}}'' after having lost a duel.
* Shinji of ''{{Evangelion}}'' many times, as well as much of the other main characters, mainly Asuka.
* In the anime series ''TsukuyomiMoonPhase'', Hazuki has frequent periods of NotHimself, during which she "becomes" Miss Luna, a lustful, blood-thirsty vampire girl.
* Aside from [[MoreThanMindControl Ken]] during ''DigimonAdventure02'', the normally nice and affable Takeru has been known to become scarily angry when there is a threat to his Digimon and friends, as a result of witnessing the [[DeadSidekick death of his own Digimon]] in the first series. These angry moments have caused him to physically attack the then-Digimon Kaiser Ken ([[http://i75.photobucket.com/albums/i320/mpcp13/TakeruDarkAmusement.jpg while smiling in dark amusement at Ken's injury of his [Takeru's] face]]), advocate the killing of Dark Digimon, and deeply disturb [[FusionDance Jogress]] partner Iori on separate occasions.
* This usually sparks the plots in HigurashiNoNakuKoroNi, but one character stands out in particular: "The person who was there was not the Rika-chan I knew. It was another Furude Rika." Of course, the difference between Rika and the other examples is that [[spoiler:the "abnormal" personality is really her true self, her "normal" self is just ObfuscatingStupidity.]]
* In {{Bleach}}, the 9th Espada, [[spoiler: attempting to trick Rukia by posing as her former mentor Kaien Shiba, betrays himself by making a request that was blatantly uncharacteristic of Kaien.]]

[[/folder]]

[[folder: Comic Books ]]

* Cosmic Boy of DC's post-Zero Hour ''LegionOfSuperHeroes'' spent a whole {{Arc}} being Not Himself and alienating his teammates at every opportunity [[spoiler: in order to set up an elaborate EngineeredPublicConfession which revealed the President's corruption and caused her removal from office]]. Some Legion fans never forgave him for it.
* Apparently, hacking into Superman's mind is like evil hypnotists’ [[WikiVandal wikivandalism]]. Some bratty six-year-old in Minneapolis trips over a ouija board, next thing you know our Man of Steel is giving the Batman a wedgie. Supes has probably been brainwashed, hypnotized, or possessed more than any character in fiction. And if you count the times he’s [[SuperDickery pretended]] to be NotHimself, more than all fictional characters combined. Read any random five Superman or Superman-associated comics from the 50s through the 70s, and see if you can’t find one of these stories.
** Or refer to [[http://www.superdickery.com/ here]] for the condensed version.
* In the ''[[JusticeLeagueOfAmerica Justice League International]]'' comic, Guy Gardner spends a rather extended period like this after minor head trauma. The abrasive, chauvinistic, arrogant Guy turns into a sweet, Sensitive Guy -- who really exists down deep, as exhibited when Guy falls in love. This trope is partially subverted, though, because the League ''likes him better as Sensitive Guy'' and therefore makes no effort to return him to his previous state.


[[/folder]]

[[folder: Film ]]

* Inverted in ''Dangerous Liaisons'', when the Vicomte Sébastien de Valmont, known to be a ruthless, womanizing manipulator genuinely falls in love with Madame Marie de Tourvel. He is forced into the situation by Marquise Isabelle de Merteuil, and with tears in his eyes has to push away the woman he loves through cruel manipulation. She is aware that it's [[SomethingTheyWouldNeverSay odd for the Vicomte to speak thus to her]], but is heartbroken nonetheless.
* In [[WoodyAllen Everyone Says I Love You]], one of the characters becomes a Republican to the great surprise (and dismay) of his family. It turns out it was because of some sort of brain problem.

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[[folder: Fan Fic ]]

* The only reason [[MyImmortal Dumbledore]] swore was because he had a ''headache'', okay? (Of course, he then swears regularly for the remainder of the "text".

[[/folder]]

[[folder: Literature ]]

* Ditzy but loyal vampire queen Betsy Taylor becomes a real bitch after reading too many pages of the [[BookOfShadows Book of the Dead]] in a row in ''Undead and Unappreciated.''
* In the V.C. Andrews novel ''April Shadows'', April's father starts to act like a {{jerkass}} to his family for seemingly no reason. [[spoiler: The reason turns out to be that he found out he had terminal cancer and he didn't want his family to feel sad for him when he died. So, he decides to make them hate him. Once April, her mother, and sister find out, though, they feel sorry for him anyway.]]
* This is one of the main plot points in the {{Animorphs}} series due to the fact that the primary villains are aliens who take over the bodies of humans and mimick them near perfectly.[[spoiler: In one book, Jake is taken over. The only reason the Yeerk fails is because of a monetary slipup in which he shouts Andalite Filth.]]

[[/folder]]

[[folder: Live Action TV ]]

* In the second season of ''{{Angel}}'', Angel turns on his friends and finds himself without hope.
** Not to mention his role in the second season of ''Buffy'', after experiencing a moment of pure happiness (ie sex) with Buffy caused him to lose his soul.
* ''TwinPeaks'' ended with a NotHimself, presumably to have been the plot of the cancelled third season. "How's Annie? How's Annie? How's Annie?!"
* ''StarTrek'' has several, mostly involving Kirk and Picard.
** Data is pretty good at them, too. Usually when he's possessed by one thing or another, or something's going weird in his programming.
** Geordi La Forge gets one of these in the episode ''Mind's Eye''. The most disturbing thing about it being that asides from his being brainwashed and attempting to murder someone in full view, he behaves entirely and utterly ''like'' himself.
* ''{{Smallville}}'' has its fair share of NotHimself episodes, no thanks to Red Kryptonite.
* ''TheOffice'', American version: assistant manager (or assistant to the manager) Dwight Schrute, a pompous, anti-social jerk, inexpicably starts acting nice to everyone. Later it is discovered to be the effect of a concussion Dwight suffered as a result of a car crash earlier in the episode.
* ''NewsRadio'': Matthew punched out Bill after one of Bill's pranks went too far. Somehow, the two [[FreakyFriday switch personalities]] - Bill becomes submissive, while Matthew starts acting like the office alpha male. An accidental slap from Bill reverses the effect, and the two return to normal.
** In a later episode, Matthew suffers a mid-life crisis after turning 30 and starts acting like a '70s-era British punk.
* On an episode of ''Kojak'', Lt. Kojak appears to go corrupt, but of course in the end it's all a [[FakeDefector big undercover operation]].
* Used to the point of exhaustion on KnightRider, where at least twice a season someone would screw with KITT or manipulate Michael for various reasons.
* ''GetSmart'': [[GeniusDitz Maxwell Smart]] is attempting to infiltrate a KAOS group, and as such needs to dramatically burn all his bridges with CONTROL. Of course, this being ''GetSmart'', it [[HilarityEnsues doesn't work quite as planned]].
* Happens a lot in ''{{Stargate SG-1}}''. Between the Goa'uld, mind control, robots, clones, and other random behavior changes, the characters get a pretty good taste of this.
* In season 5 of ''{{Lost}}'', after [[spoiler:returning to the Island]] Locke is not himself, acting more determined and secretive than ever and knowing things he can't possibly know. Because [[spoiler:he's still dead and Jacob's enemy is in his place.]]

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[[folder: Video Games ]]

* In ''Fate/hollow ataraxia'', the fact that many of the characters are nothing like they were in ''[[FateStayNight Fate/stay night]]'' is actually an early clue that something's wrong with this reality besides the whole GroundhogDayLoop thing.
* [[spoiler: Zidane]] in ''FinalFantasyIX'' displays this for a short while near the end of the game. Given his normally cheerful personality, this troper found his Not Himself moment genuinely frightening, as he hinted at [[spoiler: what he was really capable of if he had been acting towards his intended purpose]].
* In ''FinalFantasyIV'', it is said at the beginning of the game that the King's behavior changed. [[FakeKing Of course...]]
*[[KnightsOfTheOldRepublic HK-47]] can have a Not Himself moment in the second game if the player installs a Pacifist Package into him. Needless to say, [[CrowningMomentOfFunny this genuinely scares the hell out of him]].

[[/folder]]

[[folder: Webcomics ]]

* Parodied by ''[[http://nodwick.humor.gamespy.com/gamespyarchive/index.php?date=2002-05-02 Nodwick]]''.
*In ''GunnerkriggCourt'', Chapter 18, Robot S13 -- previously the comically {{Pollyanna}} ChewToy -- abruptly begins acting deadly serious and [[TookALevelInBadass proves to be a dashing swords-bot]], much to the surprise of Annie and Kat. Presumably his new body has something to do with the change, but ''how'' remains to be seen.
* In ''Fans!'', when Alisin's incurable and deadly blood disease starts to kick in, she sets out to pull an April Shadows in order to leave her loving boyfriend less sad when she goes. [[spoiler:Despite (or perhaps because of) the best efforts of the BigBad and the traitor, he not only figures it out but time travels to a period when the disease has been cured thanks to the [[MenInBlack FIB]]'s efforts to save ''her'', lets a teammate trick the BigBad into contracting the disease, and thus distracts her long enough to get some of the cure for Alisin. Everything works out- well, sort of.]]

[[/folder]]

[[folder: Western Animation ]]

* A [[TearJerker tearjerking]] example occurs in ''{{WALL-E}}'': [[spoiler: EVE repairs WALL-E after he's been crushed to death. However, once he's started up again, WALL-E has no memories of EVE, and his personality is gone. He's just another trash-compacting robot. EVE especially notices he's not himself when he regards all the trinkets he's collected over the centuries as just more trash, and is completely indifferent to the cockroach he adopted as a pet.]] Fortunately, [[spoiler: he gets better]].
* ''WinxClub'': [=4Kids=] turned Stella being a bit bitchy with her roomies from being part of her character to being the result of a spell, thus making it funnier. ([[http://www.youtube.com/watch?v=EJa5UWOJDOg Clip]]) There have been a few instances that are in both versions, though.
*Briefly in the ''DannyPhantom'' episode "The Ultimate Enemy" where Danny's [[FutureMeScaresMe evil self]], Dark Danny, goes to the past (present time) and disguises as his old fourteen-year-old self. His friends wonder what's up with him when he starts speaking rather eloquently, but being a [[ConsummateLiar smart bastard]], Dark Danny quickly fixes this and their suspects drop.

[[/folder]]

[[folder: Real Life ]]

* Several illnesses or psychological factors can lead to a person's behavior changing dramatically. One of the most well known examples would be Phineas Gage, a railroad worker who was said to have been honest and reliable prior to an accident which lead to a metal pole being ''blasted through his head, damaging both his frontal lobes''. Afterwards, he became a much nastier person. The accident shed light on the effects that frontal lobe damage can have on personality.
**Maybe it wasn't the accident. In the words of the clearly well-researched website Cracked:
-->[...]scientists have come up with all kinds of theories about the damage affecting his impulse control. But, holy crap, some of us turn into dicks after missing morning coffee. Can we not cut a guy some slack after surviving a fucking spike through the skull?
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