Inaho Hitomebore from Master of Mosquiton 99. To the school, she's the most exalted student; to those unfortunate enough to travel with her, she is a miser who uses her friends as tools and makes the guy who loves her do stupid and humiliating things while she ignores his pleas and thinks of riches.
Pokémon had an episode about this with a Teddiursa, using its cuteness to steal and fool people. When it ran into Ash's group, it stole and framed Ash's Chikorita and Totodile for what it did, and Misty was easily tricked. However, they eventually find out the truth, and when its cute charade fails to work on them again, it quickly drops the "sheep's clothing" part and just keeps on eating the food that it stole from the gang in defiance.
An earlier episode, "The School of Hard Knocks," had Giselle, a student at Pokémon Tech who bullied the younger students under the guise of tutoring, who effortlessly beat Misty in a Pokémon fight and dismissed Ash's statement that trainers have to be friends with their Pokémon, even mocking Ash's Pikachu. Ash, of course, puts her in her place by beating her with said Pikachu.
In Ashita no Nadja, Nadja's best friend, Rosemary Applefield, starts as a sweet Naïve Everygirl with a huge inferiority complex. After she's "betrayed" by Nadja and snaps, she makes everyone in her surroundings believe she is the real Nadja, fooling a whole noble clan as a part of a conspiracy that will make her boss, Hermann Preminger, the true heir to the clan. To make these plans work, Rosemary shamelessly lies, tells half-truths, manipulates, steals/destroys various stuff, and gleefully takes part in Hermann's various schemes, rarely losing her innocent facade, and even being ready to betray her boss if she gets to keep her new "princess" status that way. And even when she admits her defeat and willingly returns everything to Nadja, Rosemary bitterly recognizes that she's been so deeply changed by such experiences that she just can't be the genuinely sweet kid she once was.
Anko's wart in Episode 14 of Thriller Restaurant. When she takes over the real Anko's body and mind, she makes herself appear as a bright, attractive girl. In reality, the wart is arrogant, manipulative, and absolutely sadistic. Thank goodness Shou noticed something was wrong with her.
Lust is one briefly in Fullmetal Alchemist. As Havoc's girlfriend Solaris, she was apparently charming, sweet, and attentive, and was very supportive of him as he got used to living in Central. Havoc is understandably a bit shocked when she turns out to be an evil quasi-immortal being who literally stabs him in the back, and then goes on to try to kill Mustang, Hawkeye, and Alphonse, all the while thoroughly enjoying herself.
Let's not forget Shou Tucker. "Nina, want to play with daddy?"
Miya Miya of Bamboo Blade. In classic Power-Rangers style, she's added to the team as the "Pink" ranger for her cute and sweet nature. It's all a lie, though. She's actually the most terrifyingly brutal character in the show. The team names her real persona "Black", and it comes with its own aura of violent intent. On one occasion, it startles Pink Miya Miya when just her grimace from painful feet terrifies Sayako and Kirino into dogeza because they think "You were Black Miya Miya!"
Polly (Pururun) from Samurai Pizza Cats, while sweet and charming at first, is actually a real bitch when she gets annoyed, often taking her frustrations out on innocent customers.
Sei Arisaka from Himechan No Ribon acts like a perfect gentleman towards everybody around him but Daichi seems to be the only one who realises he has an alternative motive.
Shou from Skip Beat! has carefully engineered his public image to look like the perfect Teenager Cool Prince, and he isn't shy to step over anyone he considers beneath his "grand destiny" of becoming the most popular artist in Japan. He is also selfish, immature, petty, absurdly self-centered, and completely unable to cope with any reaction which isn't admiration or adulation.
Tomoe Marguerite from Mai-Otomeputs on airs of sweetness in front of the staff at Garderobe, but has no problem hurting or otherwise manipulating others to get her way, especially when Shizuru is involved. She even acts nice to Arika herself (in her mind, her main rival for Shizuru's affection), but mainly while others are watching, and reveals her true colors to Arika when she first sees her after the Wham Episode.
Sakurako Sanjou of Hana Yori Dango, who, in all continuities (manga, anime, drama), befriends Tsukushi Makino and looks like a kind, shy, cutesy type...at least up until she has Tsukushi drugged, takes pictures of her unconscious, in compromising positions, and distributes them freely among the school, leading to her assault by other students. This is revealed as a part of her master plan for seducing/exacting revenge upon Domyoji, Tsukushi's Slap-Slap-Kiss-y love interest, which also involved her spending a fortune on plastic surgery, dropping out of school in the past, and hiring professional goons to assault various characters (not only Tsukushi). The reason for all of this is that ever since she was in kindergarten, Domyoji bullied her and called her ugly. Talk about one Woman Scorned.
Sousuke Aizen from Bleach would be a male example of the trope. Actually, he's probably the best example of the trope, because he's actually the Big Bad. And prior to his introduction, he spent at least a hundred years maintaining the nice guy façade.
Natsu Tanimoto of Kenichi: The Mightiest Disciple is another male example. To most of the school, he's the extremely handsome, incredibly intelligent, multi-talented, kind-hearted honor roll student. To the members of the Shinpaku Alliance, however, he reveals his true nature: an angry, violent, short-tempered Jerkass who is prone to stomping them into the ground for even looking at him the wrong way. However, thanks to some Character Development (most of it courtesy of Kenichi's little sister Honoka), he's now more of a Jerk with a Heart of Gold, though you'll be hard-pressed to get him to admit it.
Sae from Peach Girl, who uses her Raven Hair, Ivory Skiningenue appearance as an advantage over "gangster-looking" Dark-Skinned Blonde Momo (she tans easily). Out of jealousy that Momo has the attention of two hot Bishounen classmates, Sae pretends to be her friend but starts whispering rumours about her, repeatedly pulls the Wounded Gazelle Gambit to make people hate her, blackmails her mutual crush into pretending to be Sae's boyfriend instead to protect her, and tells her (next) boyfriend that Momo has rape fantasies about him and demands that he fulfills them - then tricks Momo into going somewhere with him, and drugs her into a stupor. And this was just what she'd done by the 2nd volume.
In a not-uncommon Hentai example, Yuriko from Moonlight Lady. At first, she seems to be a Yamato Nadeshiko who honors family tradition. She is. She just doesn't care that her daughter gets raped as a part of it. She's not above trying to steal her son-in-law-to-be, either.
Doe-Doe Eun of Pig Bride is publicly a sweet Yamato Nadeshiko maiden who enjoys being demure and needlework. But it's almost entirely an act to snare the main lead, who has made no secret that that's the kind of girl he likes. When there are no boys around, Doe-Doe is a ruthless gangster-type who bullies the other girls so they won't move in on her territory. What makes her a touch more sympathetic is that she is stuck in a You Can't Fight Fate competition with the title character, rendering all her efforts fruitless from the start.
Akira of Samurai Deeper Kyo fits this trope in his interactions with Yuya. To the male characters, he's a complete and utter bastard, but to Yuya, he continues to act sweet even after she knows it's an act.
A more classic example in the series would be Antera, who has the appearance of a young girl but once killed a man by squeezing his head until it popped.
Ran from Urusei Yatsura, although a bit on the Yandere side. Ryoko, on the other hand, is a better example.
During the introduction story of "Pantyhose" Tarou, when Shampoo finds Akane alone and tied up in a cave, she thinks that this is a perfect opportunity to Murder the Hypotenuse and let Tarou take the blame. While she was initially quite blatant and straight-forward in her attacks on others, by this point in the manga, she had become quite duplicitous.
Lunar appears to be a sweet, incredibly MoeIdol Singer. Turns out, she's really a bit of a bitch, especially when it comes to one-upping San. Although she does have some genuinely nice moments.
Maki's character design was basically created to embody as much Moe as possible, her being an eight-inch-tall Shrinking Violet. Then she turns out to be a Yakuza Enforcer who spends the bulk of the series attempting to kill Nagasumi, who she despises, all while keeping up the cute facade so his fiance doesn't catch on.
C.C., who at first seems like a persecuted Mysterious Waif with a humorous affinity for being a Deadpan Snarker when it comes to Lelouch and a love for pizza. But as the series progresses, it's revealed that she seriously FUCKED over her insanely-obsessed lover Mao, Lelouch's predecessor, in fact, and is running a particularly cruelThanatos Gambit to direct Lelouch into fulfilling her secret death wish so that she doesn't have to live anymore. Oh, and that guy named Mao? She tried to do the same to him first, but because he was her Yandere, he refused, and she abandoned him for it. Complete with incontinenttelepathy. Nice. Although, around this point it's revealed (that she abandoned him because she cares about him too much, in hopes of getting him to get over him; she's not capable of killing him, until he starts seriously trying to kill Lelouch and Nunnally; is later revealed to have once been a Woobie who, thanks to her "Love Geass", forgot how to be loved and wanted to be free of her curse to find it again, but was betrayed by her own Bitch in Sheep's Clothing, and in the end forsakes her Thanatos Gambit and accepts living.
Asuka Langley Soryu is an inversion of this trope. She is a Tsundere acts mean to many characters to hide her feelings and her real self because she is convinced nobody would like her. But she sincerely tries to be deredere sometimes. Usually only to Kaji or Misato, but also to Shinji sometimes. For example, she pretended to kiss Shinji just to pass time, but actually, she has feelings for him.
The manga plays it much straighter, having Asuka put on a facade of the "perfect good girl" around the adults but reverting to her normal self otherwise. Eventually, Misato tells her that she isn't as good an actor as she thinks she is, and she has no need to put up the act around them. Asuka drops it from then on.
Jin in Innocent Venus. he actually manages to keep the act up for half the series, honestly appearing to be a Nice Guy with only the occasional slip-up (and a scene in the opening) to hint that he's not the main protagonist, but is, in fact, an outright villain.
Yukino from Yakitate!! Japan. The first time she appears outside of a flashback, she acts very friendly to Tsukino and apologizes for defiling her mother's ashes. It's all a lie, but this facade has her grandfather wrapped around her little finger.
Shinghi from Zippy Ziggy, especially at first. It's pretty much the entire point of his character. The same with his father.
Surprisingly for a harem story, Hayate the Combat Butler has three, all seeming to be on the same side of the good vs evil line. All three seem to have taken up this because of love, but don't have the mental instability of a Yandere.
Athena is the strongest case, at least as a little girl: she acted wonderful and loving to Hayate, even training him to be stronger, but any time she got a hint of him not being single-mindedly in pursuit of her, she didn't hesitate to attack, usually Hayate himself. She appears to have grown out of it.
Mikoto (Wataru's mother) also seems harmless, but uses wiles to try to convince/coerce Wataru to live with her while belittling both Saki (his maid) and Sakuya (one of his potential love interests).
Mikado seems to be acting this way, an unassuming old man, but with significant evil intentions just under the surface.
Honey Hunt: Yukari is Yura's mother, a beautiful and talented actress. But her beauty is only skin deep, as shown throughout the series. She is never at home for Yura and is very selfish. On all of her interviews, she lies and says that she and Yura are close and spend much time together, when in reality, she is a cold and distant parent. While her husband was having an affair, she was having one of her own with Yura's neighbor, Shinsuke (who Yura had a crush on). She and her husband were only together for the sake of their careers and their images, they didn't love each other. The two of them even agreed on a rule with each other that they would stay married as long as they hide their own adulterous affairs. After she decided to divorce Takayuki, however, it is shown that she has no intentions of taking care of Yura, and only cares about improving her image in the eyes of the public who had originally thought she was the "ideal mother".
Hana Mizuki from Papillon. She has a beautiful angelic appearance and acts in a sickeningly sweet manner towards people, but underneath that is an extremely manipulative and selfish girl who acts terrible to her sister for the sole reason that she wants to prevent her sister "from ever attaining happiness" out of jealousy that boys seem to like her sister's personality more than hers. Kyuu compares her to a rose, stating she is "covered in thorns".
Mayu Okada from Kaguya Hime. She is very much a Yandere for Akira, and doesn't let men or women near her. She has a sweet appearance but, beneath that, is very manipulative and will do anything to get her way, such as pretending to be sick and fainting on the spot to get attention.
Mimi Yoshioka from Lovely Complex. She is in love with Otani, and brings him milk every day so he could reach her height, about the same as Risa's. Since Otani does not have feelings toward her but does have feelings for Risa, she becomes jealous of her. She acts accordingly two-faced between them both: acting sweet and cute whenever Otani is around, yet slipping into psycho mode and acting malicious to Risa whenever Otani is not around. She becomes less of a jerk later on, though.
Oniisama e...: Fukiko and most of the senior members of the Sorority. They'd sell their grandmothers if it would bring them the slightest advantage (after inviting her to a fancy dinner, nonetheless).
Heloïse Villefort of Gankutsuou. She seems perfectly normal in her first few appearances, with a warm motherly appearance and pleasant smile. She is the stepmother of Valentine and is the second wife of the crown prosecutor Villefort. She is the biological mother of her young son Edward, from her first marriage. Valentine is to inherit all of the fortune, leaving her stepmother jealous because Edward doesn’t get a single penny. So when the Count seduces her and innocently introduces her to toxicology and gives her a deadly ring which releases poison, Heloïse becomes murderous and tries to poison Valentine and her husband, as well as inadvertently almost poisoning Albert and one of the servants of the Villefort household. And she does all this while maintaining her angelic motherly facade up till near the end of the series when her husband finds out what she's been doing and points out that she's nothing more than a murderous woman who's completely lost it before he sends her to an insane asylum.
As well as Andrea Cavalcanti aka Bendetto. He briefly seems to be a highly cultured fop and a decent guy, and continues to put on that persona, but he's really a total psychopath.
Naruto: Kabuto Yakushi. He usually presents himself as this harmless, bumbling oaf with Nerd Glasses who showed up to help Naruto and his teammates on occasion but is, in fact, a sadistic Manipulative Bastard and a subordinate of the Big Bad Orochimaru.
Elfen Lied: during Lucy's childhood, she made friends with a seemingly sweet, kind-hearted girl who promised to keep the fact that Lucy was taking care of a puppy a secret from a group of boys who frequently bullied her. Eventually, the boys find out about the puppy and beat it to death in front of Lucy while making her watch. Turns out, the girl Lucy made friends with had deliberately told the boys about the puppy, and while she's pretending to cry about it and feel bad about what she did, we see her smile through her tears. Lucy then snaps and kills her along with the bullies.
Captain Shears in the Star Fox comic "Farewell, Beloved Falco" - Shears, a military officer on Titania, tells Fox that he needs help combating remnants of Andross's army who are planning a counterattack. In fact, Shears is trying to re-build Andross and is trying to fool Fox into attacking Falco and his group
Seto Kaiba, in his first appearance in the manga and the first anime, pretends to befriend Yugi, and has Yugi's grandfather's Blue Eyes White Dragon switched with a copy. When Yugi figures this out and calls out Kaiba on the switch, Kaiba loses the facade and whacks Yugi in the face with a briefcase.
Kaiba does it a second time during Death-T in the manga. He pretends that he has forgiven Yugi and simply wants to let him and Jonouchi have a good time; once Yugi discovers that his grandfather is in the battle arena, Kaiba drops the pretense of being nice. Yugi notices the difference in how he acts around a disgruntled ex-employee and how he acts around him, but doesn't suspect enough to see through him until it's too late.
Nezumi in the manga - Yugi and Jonouchi meet Nezumi at school. Nezumi claims that a gang of bullies attacked him and that he needed help in dealing with them. In fact, Nezumi was ordered by Hirutani, Jonouchi's old middle school friend and now enemy, to have Jonouchi and Yugi lured to the abandoned warehouse so that Jonouchi could be forced to re-join Hirutani's gang.
Volume 1 and Season 0 had Ms. Chono. To the teachers and staff, she is just an incredibly nice and beautiful teacher who does incredibly well in getting her students to behave, and the only flaw she has is her not-so-suspiciously-poor track record for arranged dates and marriages always being called off. To the students, however, she is the "wicked witch of expel", who noticeably has as much bitchiness as she does make-up on her face, and who expels students for even the slightest twitch and has taken delight in starting dates with men just to tug at their heart strings and then shatter them to pieces. Yami Yugi reveals her true nature, but how he does so varies between the manga and the anime.
IV Arclight from Yu Gi Oh Zexal. When near his fans, he creates a facade in which he is very polite and respectable, while in reality, he's extremely sadistic and cruel, to the point of where he showed a young child being tortured via a television screen to his older brother just to see his emotional pain during their duel.
Ayumi in Gu-Gu Ganmo. She appears to be a cute, gentle girl in the first few episodes, but eventually, she shows her true colors and turns into a manipulative, self-centered, and aggressive little bitch. Oh, and her farts could wipe out whole towns.
Henri from Future GPX Cyber Formula. For most of ZERO, he appears to be a cheerful rookie who seems to be nice to most of the racers, but in reality, he's a vengeful person who wants to make Hayato suffer for taking away his dream. His father was a former racer who pushed Henri to be the best in racing to make him the youngest champion in CF history, but when Hayato got the title before him, his father started drinking and then abandoned him, which triggered his resentment towards Hayato. He mellows out at the end of ZERO.
Fiore of The World God Only Knows is actually introduced to the audience as an agent of Vintage from her first appearance, and it isn't until after she stabs Kanon that we see the sheep's clothing that she wears around her fellow New Devils.
In Bakuman。, ToruNanamine acts polite and cheerful around the editors, apologizing for publishing his oneshot online after it got passed over for an award, and the main characters note that he seems somehow overly polite. When he's alone with the main characters, though, he reveals that he has nothing but contempt for editors, who he views as outsiders who know nothing about manga. He keeps up his persona around his editor until he reveals that he is corresponding with 50 people online for ideas, and, while taking advantage of his editor's lack of confidence and need to get a series, threatens to go elsewhere if his editor doesn't go along with what he does as the 51st person.
Johan Liebert is one of the most pleasant and polite people imaginable. He's incredibly classy, cultured, intelligent, and a very good listener. He's also practically the embodiment of pure evil. All of his "nice actions" just make it easier for him to get into your head, Mind Rape you, and either kill you, get you to kill others for him, or make you kill yourself.
Faux Action Girl Miko, the cute, helpless strange girl and cuddly and cheerfully friend in need who drove Aya to the whole mess? Nothing but a bitchy mark.
Heterosexual Life Partner Natsume, Aya's best friend forever? Actually a revenge-obsessed bitch willing to trample, maim, and Mind Rape a whole bunch of innocent women and girls just to screw with Aya. The whole time faking friendship towards her just to rub it in her face during The Reveal.
Natsume's brother, Aya's love interest? Ruthless enough to kill in cold blood people he actually hired for his plot, is Miko's lover, and in league with the other two to ruin Aya's life forever.
Natsume's mom, the epitome of the trope. Currently a Cute Mute mom, secretly a Stepford Smiler, deeply inside, a raging beast that, due to have catastrophically lost her voice, mental sanity, and freedom because of Aya's mom when both of them were plucky Action Girls (and she actually tried to kill her opponent's parents, it seems...), masterminded the whole convoluted plot, pressuring her offspring and their cousin Miko to send dozens of young girl to same fate as her just to ensure Aya was reeled in.
Kimi No Iru Machi gives us the character Eba Rin, main heroine Yuzuki's younger step-sister. Even before the manga begins, Rin has managed to make her sister so uncomfortable that she moves out to be as far away from Rin as possible. Eventually, she drops her meaner tendencies and gets along with her sister, but still loves to troll just about everyone else.
In the story Monsters of One Piece Wanted, we have Cyrano. He seems to be a nice guy at first, but he's actually a huge asshole.
From the main manga we have Caesar Clown. He acts nice toward his subordinates (as well as the kids on his island), but in truth he couldn't care less about them and isn't above experimenting on them, intentionally getting them hooked on drugs, or even ordering their deaths if he has reason to.
In a more general sense, everyone who took young Robin in after the Ohara incident was this, as they only took her in so they could sell her location to the Marines and get the bounty that was on her head. As if doing that to a child wasn't already horrible enough, some of them even had the balls to claim that it was Robin who was being ungrateful, repaying them for their kindness by running away.
In Revolutionary Girl Utena, Nanami comes off as one of these in her first episode, presenting herself as a potential friend for Anthy before setting her up for humiliation at the ball. More prominently, Shiori's quiet, polite demeanour hides extremely bitter feelings towards her childhood friend Juri.
Masahiro from the manga Teacher's Pet. He's aggressive and forces sex onto the protagonist several times but he's quiet and feminine looking so no one guesses it.
Momoka from High School Girls: Jealous of her older sister Yuma's friendships with the other main girls, she spreads a rumour that Ayase is cheating on her boyfriend, leading Ayase to assume it was Yuma and cause them to fall out, gloating about how it only took her spreading one rumour to shatter one friendship and how it would only be a matter of time before she destroyed the rest, all whilst pretending to befriend the other girls and generally behaving in a cutesy, peppy manner. Luckily, Eri figures it out.
Asakura Ryoko from Haruhi Suzumiya is the friendly, polite, attractive, class representative who always has a kind word and a smile... until she tries to stab Kyon because she's bored and she thinks killing him will get Haruhi to do something interesting.
Emiri Kimidori fits this as well, as she doesn't give damn when Nagato is made ill by contact with the Sky Canopy Dominion. This causes Kyon to call her a "monster" like Asakura. Basically all the IDSE interfaces except Nagato.
Masato Kadowaki from Arata Kangatari, who acts like a typical nice guy in front of everyone on his first day. The facade doesn't last very long, as he already resumes bullying Hinohara like he did in middle school within the first few days.
Kyo Koi O Hajimemasu: Poor Rika seems so nice, timid, fragile and innocent...until we find out she uses her apparent weaknesses to sleep around, manipulate people and set herself as the victim, all the while laughing at the others' expense.
When Nurakami first meets Nanami in Kamisama Kiss she acts like she wants to do her a favor by taking over her position as a land god and removing the burden of responsibility from her. Really, she is just trying to claim Nanami's familiar, Tomoe, as her own and once Nanami says no she stops acting nice.
Hiyori initially hates how Haruka seemed to swipe Manabe from her, so she tries to alienate and bully her in episode 2. Once Manabe realizes what's going on, he confronts her about it and calls her out on her bullying. Although later she had a change in heart, and wished Manabe to be happy instead.
This is how Yuriko presents herself as to Dai'chi, but he points out plainly that she's just fooling herself in thinking she's that cold-hearted. While she does have a partially hidden agenda regarding Haruka (presumably to make Haruka well-known as a psychic in order to vindicate Yuriko's mother), she still seems to care about her greatly.
Camilo from Romeo X Juliet. He seems to be a nice man and a good friend for Conrad, but he really turns out to be a Smug Snake, once he showed his true colors by giving information on the Capulets' hideout towards the Montagues.
Lebreau Fermet Viralsque. He appears to be a nice, calm and loving figure. But his true nature is of a cruel sadist who tortured Czeslaw Meyer for a couple of centuries; he's the mastermind of the tragedies of the 1700 arc, killed Monica, Huey's wife, and is the responsible for all the bad stuff that happened to the immortals.
Chuunibyou Demo Koi ga Shitai! has Shinka Nibutani, who seems to be a sweet, friendly, responsible Yamato Nadeshiko class rep... She's actually a (semi-)reformed Chuunibyou with a violent, selfish temper who's trying desperately to be 'normal'.
Fujisaki from Oneechan Ga Kita acts this way initially, although she has a Freudian Excuse, since she was bullied as a kid, and boys treated her with contempt even when she tried to be nice.
Surprisingly, Sonic the Hedgehog fits this trope in the Fleetway comics. While he was hero worshiped by all of Mobius as a fearless symbol of hope, he was actually a self-centered, immature Jerkass. This comes back to bite him in the ass in Sonic The Comic Online, where the sheep's clothing gets flung off and he ends up becoming a fugitive. Once the public knew about some of his more questionable decisions that he made to try and save Mobius, all the Jerk Ass tendencies that people were willing to ignore made it easy for Grimer to convince the public that he was a villain.
Dean in My Faith in Frankie. Although he gives the excuse of being in Hell for ten thousand years during the day he spent dead, the very fact that he ended up in Hell implies that he was actually always like this, and now he just has a focus and outlet.
At his very worst, Cyclops of the X-Men (of at least a Darker and EdgierAnti-Hero in The Cape's clothing), in contrast to Jerk with a Heart of GoldWolverine. Ignoring the complicated mess that is his love life, Cyclops tries to project the image of a wise and noble leader for mutants to admire while keeping dirty secrets from his teammates, such as the existence of X-Force, his personal mutant kill-squad. This is after he kicked Professor Xavier out of his own home because he kept secrets from Cyclops. To be absolutely fair to Scott, he really thinks all of this is necessary to ensure the survival of mutantkind after the various disasters of the past few years — and he might be right. Still, at one point, Wolverine, X-Force's field leader, reminds Cyclops that his hands are just as dirty as any member of X-Force's, since Cyclops organized X-Force in the first place and gave them their orders.
Thessaly of The Sandman. She may look like a sweet young college-age girl, but in reality, she's a paranoid, millennia-old witch with a nasty habit of offing anyone who so much as annoys her.
Indigo of the Outsiders was a strange variation. She started off as a seemingly-homicidal robot, then got "reformed" into a cute Robot Girl, before finally being revealed as the latest incarnation of Braniac.
Iznogoud tries to be this toward the Caliph. He is terrible at it, but the Caliph is so oblivious it still works anyway.
Many Wicked Stepmother fairy tales involve the stepmothers acting nice to the stepchildren when their fathers are still alive, and then turning cruel after the fathers pass away. This may also apply to the father if the stepmother was always motivated by desire for money.
A Growing Affection: Homura appears to be the most kind and reasonable of the three Konoha elders. Turns out he was Gouki's man almost the entire story.
A Future of Friendship, A History of Hate: When Regal Rule is introduced in Episode 4, he at first appears to be Rarity's long-awaited Prince Charming, but it soon becomes apparent to the reader that he's trying to drive a wedge between her and her friends. And then he turns out to actually be Megalos Tyrant, one of Ruinate's heralds (specifically, the element of arrogance).
An Alternate Keitaro Urashima has Granny Hina, who tries to pass herself off as a Cool Old Lady who's only got everyone's best interests at heart when she's really a Manipulative Bitch. Her true colors emerge when she doesn't get her way, and much of the conflict is spurred on by her attempts to force others to do what she wishes against their will.
The starter boyfriend of any female lead in any Romantic Comedy. Sometimes, the nice guy veneer is so thin, you have to wonder HOW he manages to hide it at all from the woman, or why he even WANTS to marry her instead of just dumping her and moving on to the next girl?
The mermaids from Pirates of the Caribbean: On Stranger Tides - for such sexy, harmless-looking creatures, they sure are vicious.
The Chronicles of Riddick: William J. Johns at first appears to be a clean-cut lawman and typical hero, but soon reveals himself to be a scheming weasel with no concern for anyone but himself.
Fairy Godmother from Shrek 2. We assume all fairy godmothers are nice - this one definitely is not.
The Bishop Edvard Vergerus from Fanny And Alexander by Ingmar Bergman. He seems fairly benign, if a little self-righteous, before pulling back the curtain to reveal a true sadist, justified by piety.
The Harry Potter flicks have both Quirrel and Umbridge, who both seem quite benign on the surface, but are in fact quite evil. Heavy emphasis on the "bitch" part in the latter's case.
David Simms in Tin Cup. Partly subverted in that Roy MacAvoy and all his friends already know this about David. Conversely, David's girlfriend (with whom Roy falls head-over-heels in love, naturally) doesn't realize that Roy's comments about David's true nature are accurate until the movie is almost finished.
Simms is even dignified in romantic defeat. He's a nice guy and a complete asshole.
Cruel Intentions: KathrynMerteuilsets herself up as a model student, a popular, well-adjusted young woman, and a devout Christian, but in reality, she's a narcissistic, alcoholiccokehead of an Alpha Bitch who regularly goes out of her way to manipulate people and destroy their reputations and lives For the Evulz. By the end of the first movie, Annette and Cecile, two girls whom she had manipulated, circulate copies of her stepbrother Sebastian's journal, in which he had detailed Kathryn's true colors, to the public, flinging off the sheep's clothing.
Regina from Mean Girls. Towards the very beginning, we're told that she's a bitch, but she seems to act perfectly civil to Cady. Then, of course, things begin to go downhill. A good example is when Regina insults someone's skirt after saying to the person's face that she liked it. This is obviously a call back to earlier in the film when she complimented Cady's bracelet.
Cady herself becomes one of these toward Regina and her circle later in the film. A case of Pay Evil unto Evil given Regina's actions, but Cady's actions (turning her friends and on-again-off-again boyfriend against her, giving her "diet" bars that cause her to gain weight, attempting to publicly humiliate her) are still quite nasty, especially since she does them under the guise of friendship.
In the Arnold Schwarzenegger comedy Jingle All the Way, Phil Hartman portrays his next-door neighbor, who appears to be a nearly perfect man: a devoted single father who dotes on his child, a master at cooking and home repair, and has a seemingly limitless supply of free time to devote to helping others. For most of the film, only Arnold can see him for what he really is: a Smug Snake whose every move and thought is dedicated to seducing every woman he comes across, whether they're single or not.
It's very heavily implied that she's doing it to deal with her own loneliness, and they do make up at the end
Karl in Blackout. On the outside, he's a helpful, chivalrous Nice Guy, devoted parent, and recovering widower. But between his flashbacks, and his gradual loss of patience in the elevator, we learn that he's a deeply sadistic and misogynistic Nietzsche WannabeSerial Killer/rapist who staged his wife's suicide, and whose main reason for needing to escape the elevator is to clean up his bachelor pad before his daughter arrives and sees the corpse of his latest victim.
In Legally Blonde 2, the senator (played by Sally Field) is sweet and kind to Elle, becoming a mentor and friend quickly. She throws Elle under the bus the first chance she gets to gain a political edge.
Mother Gothel in Tangled pretends to be Rapunzel's loving mother, but in actuality, she was the woman who kidnapped Rapunzel as a baby because her hair was full of magic from the flower used to de-age Gothel that got crushed into medicine for Rapunzel's real mother, the queen.
Carrigan Crittenden in Casper. She's this way up to the point of her ethereal death by light.
Professor Catalan in the French action-comedy That Man From Rio, a mousy, academic archaeologist who is kidnapped by folks who had just stolen a Mesoamerican statue which is the key to a vast treasure. The protagonists rescue him around mid-film, unaware that he'd staged his own kidnapping and is after the treasure himself, along the way, murdering a former colleague and abducting a young lady he had been a surrogate 'favorite uncle' to.
Palpatine, full-stop, combining this with Villain with Good Publicity. As the Chancellor of the Republic, he had cultivated an image of himself as a kind, tea-drinking, grandfatherly figure who cares deeply for his planet, The Republic, and democracy. All the while, he was running the Separatist forces as his alter-ego, Darth Sidious. Immediately upon being confronted by the Jedi, he shows his true colors as a sadistic, megalomaniacal, power-hungry Manipulative Bastard. In the public eye, he kept up his former facade, while using his new hideously deformed appearance to pull what was essentially a giant Wounded Gazelle Gambit and turn the Senate and public opinion against the Jedi.
What's more is that even after the Empire unleashed the full force of its tyranny on the galaxy, he remained popular, and even those who hated Imperial rule generally did not see him as the villain. He continued to be seen as either the galaxy's benevolent hero who ended the Clone Wars, or at the very worst, as a weak-willed old man being manipulated behind the scenes by the likes of Tarkin and the Moff Council. Very few actually realize (or want to believe) that he is a megalomaniacal tyrant in complete control of The Empire.
At one point, Mon Mothma even calls him this trope.
Ms. Quickly, to whom the father reluctantly proposes in Nanny McPhee because he must marry by the end of the month or be cut out of his wealthy aunt's estate. She puts on a sweet front until the day of the wedding, when she coldly informs the children that they're all to be shipped off to boarding school at the first opportunity.
In Three Men and a Little Lady, Mary's mother is on the verge of marrying one of these, completely unaware that her husband-to-be loathes her adorable child.
Welcome To The Dollhouse has the tutu-wearing Missy. All she has to do is dance around clumsily and the parents are under her spell. Which pisses off Dawn no end.
Red Riding Hood Prudence big time. When Valerie is chained up in the center of town, wearing a wolf's mask, and is being used to lure the Werewolf to his doom, she decides to say some spiteful things to her. Instead of apologizing to her for what was happening to her, she says that she deserves to be killed by the werewolf. She even hints that she might have been jealous of Valerie for a long time.
Frozen gives us Prince Hans, who, in contrast to the Nice Guy façade he puts on for most of the film, turns out to be a Manipulative Bastard of some magnitude, whose plan is to marry Princess Anna, with whom he fakes Love at First Sight, then arrange for an 'accident' to befall Queen Elsa, making him King of Arendelle through his wife.
Holly Jones from Prisoners. She's initially just an irritated but essentially good-natured mother trying to protect her son. It's all just a facade and she's actually a kidnapper and murder of children who did it all, along with her husband, to "crusade against God".
Detective Mark Hoffman of the Saw series. Outwardly, he presents himself as a hard-working, responsible, caring figure of law. It can fool you if one's not aware that Hoffman's a ruthless, manipulative, and murderous Dirty Cop as well as an apprentice of Jigsaw.
Blanche Ingram in Jane Eyre coos and fawns over Mr. Rochester to the point where it almost sickens the reader — though the company takes it as proof of her love — while giving Jane death glares and making cutting remarks that manage to sound innocuous while obliquely insulting Jane. Her love of Rochester, however, is put to a quick end when he tells her (lying) that his fortune is far smaller than she thought it to be.
Bronau, the wayward prince in Daughter of the Lioness is a Balitang family friend who once courted Winnamine. He and Sarai are quite attracted to each other, but he's a gossip and makes racist remarks in his flirting when the Balitangs (who are not racist) are trying to get along with the locals. Then, he starts plotting against his brother and sister-in-law and tries to abduct the child king. When that fails, he attacks the Balitang estate and kills Mequen in an attempt to make Sarai marry him.
Imajane and Rubinyan put up a good front of being Reasonable Authority Figures when talking to the Balitangs in person. Piss them off—especially Imajane, who's the daughter of previous insane king—and you'll be nailed to the docks with your kids thrown to the piranhas.
Caroline Bingley in Pride and Prejudice. Wickham is a male example: he seems like a wonderful, charming guy, but he's The Casanova and a bit of a con artist.
Lucy Steele in Sense and Sensibility. She might seem like a harmless ditz at first, but she turns out to be grasping and passive-aggressive; knowing that Elinor Dashwood and Edward Ferrars were close, she makes a big point of talking about her engagement to him in front of Elinor. Elinor being the way she is, just sits back and takes Lucy's nastiness, but deep down she's hurting, and badly. Good thing Lucy ends up with Edward's brother instead...
Willoughby as well, who is perfectly charming on the surface but a complete bastard underneath, actually worse than Wickham by a large margin.
Tommy Toledo in the short story "I'll Never Stop Loving You, Tommy Toledo" by Ellen Conford.
Darth Zannah sort of qualifies. In Dynasty of Evil, she makes an act of being nice to people just to get favors, and she seduces a guy in book 2, resulting in his death.
Given the Sith philosophy towards self-realization, which means first fulfilling one's capacity to experience genuine affection, friendship, passion, and love (thus, directly rejecting the Jedi concept of detachment), and then attaining personal liberation and fulfilling one's capacity to experience pain and loss by betraying the objects of such affection in the deepest imaginable ways...really, not only does this come with the territory, Bitch in Sheep's Clothing is probably the best outcome which can be hoped for.
Dolores Umbridge in Harry Potter and the Order of the Phoenix. Uber-feminine pink frills, kitten pictures, and passive-aggressive personal style go with an obsession with personal and governmental power. The bitchitude is meant to be transparent to the reader and sympathetic characters, but the intended hypocrisy is clear enough. Her inner bitch is meant to be out of the closet by the time she uses a magical instrument of torture on the hero.
During his school years, Tom Riddle is this. While Dumbledore can see through his facade, likely because he had seen Tom without it back at the orphanage, everyone else believes him to be an honorable, hardworking student, and a hero who caught the Heir of Slytherin.
Spock's World portrays T'Pring as this. Outside, she is extremely attractive. Inside, she is behind much of the stirring up of the anti-human bile which is pushing Vulcan toward secession.
Burgo Fitzgerald in ''Can You Forgive Her?" (1864) by Anthony Trollope. Trollope included many others in his other novels.
Male example in The Graveyard Book. Mr. Frost is the nice bachelor who has recently moved in. He is friendly to both Scarlet and her mother. Turns out, he's also the same Jack who killed Bod's family all those years ago, and is still out to get him.
Dame Olga from Ella Enchanted. When we first meet her, she seems nice enough, at least compared to her daughters (especially Hattie). But once she marries Ella's father and discovers that he had no money, she quickly turns into the cruel, abusive, petty stepmother we know from the Cinderella tale, making Ella a slave in her own home and tormenting the girl after her father leaves for business.
Grandmother in L. M. Montgomery's Jane of Lantern Hill. She's a sweet-looking little old lady, but sabotages her daughter's marriage, and can, and does, make anything sound like an insult.
The In Death series: A number of the murderers can qualify as this. A notable example would be Ava from Strangers in Death. Eve actually refers to the act Ava puts on as a suit, and Eve has to poke at it to eventually make Ava drop the act.
Sisterhood Series by Fern Michaels: Rosemary Hershey was supposedly this, but by the book Sweet Revenge, her little act has apparently worn thin. Little Fish, Stu Franklin, and Henry "Hank" Jellicoe are revealed to be this by the book Cross Roads. The book Deja Vu simply expands on the depth of Jellicoe's depravity.
Jeremy Jason McCole in Animorphs. He seemed all nice and awesome on camera but was a total jerk off camera.
Clive Barker's Abarat series contains a truly spectacular example, in the form of Princess Boa. The world she comes from (yes, more or less the entire world) remembers her as someone who was inhumanly kind, innocent, and noble. Absolute Midnight reveals that, boy howdy, sheisnoneofthesethings.
In the Agent Pendergast novels we have Diogenes Pendergast. To one who doesn't know him (so pretty much anyone but his brother) he often initially pretends to be very sympathetic or one of the nicest guys on the planet... before leading his victims on to eventually brutally murder them or put them through severe mental damage. And that's not even considering all the times he pretends to be Reasonable Authority Figure in the museum Hugo Menzies...
There's also Captain Mason in The Wheel of Darkness: Second in command of the cruise ship the Britannia who always puts the well being of its passengers first and foremost. You'd never think that she was a ruthless Serial Killer horrifically slaughtering those same passengers on your first glance.
Mercedes Cook of the Kitty Norville series is this. When first introduced in Kitty and the Silver Bullet she appears to be a genuinely kind, funny, warm, and surprisingly human vampire who, once she's decided to "come out" to the public, has a candid and revealing interview on Kitty's show where she seems to be a kindred spirit, a great face for positive human-supernatural relations, and a possible ally. But after she invites Kitty over to her hotel room, only for it to turn out to be a set-up just to provoke a conflict between her and the antagonistic werewolves (her former alphas) who exiled her back in book one, she is revealed to be nothing like either her stage persona or how she appeared on the show—instead being a cold, manipulative, calculating creature whose motives are opaque and whose intentions are inscrutable. By the end of the book she's unequivocally a villain and major threat to be dealt with (or as Kitty puts it later, a "double-crossing fink"); as of book ten she's turned out to be a recruiting agent for and possibly The Dragon to the ultimate Big Bad of the setting, Dux Bellorum.
Live Action TV
Bad Girls had Natalie Buxton. She was introduced to both the viewers and the other characters as a nice-as-pie, meek, timid woman who wasn't in jail for much of a crime. Turns out she's a peadophile with a tendency to beat the crap out of people if she doesn't get her own way. She eventually becomes the Top Dog because everybody is too scared to challenge her.
Similarly, Khan seemed like a really swell guy, til he set out to kill Kirk, steal his ship, and conquer the known universe.
The episode "Amok Time" gives us T'Pring. More of a bitch in Emotionless Girl's clothing, really, but still the ex-wife from hell whose Jerkass moves include: provoke a situation knowing that she will get back at him and it will literally kill him (given the situation, her choices would be perfectly understandable if it was, even partly, for other motives, but it is apparently only for this), trying to make him fight his captain and his friend to the death, then revealing that even if Spock still wanted her after all that, she would have cheated on him anyway.
On Star Trek: Deep Space Nine, Vedek (later Kai) Winn: wise and benevolent religious leader on the outside, but full of biting, passive-aggressive insults that quickly reveal the depths of her envy and pettiness.
Odo's former mentor, the Female Changeling, first appears in "The Search" as a wise, serene woman who is delighted that Odo has returned to his people. She and the other Founders are later revealed to be the rulers of the tyrannical Dominion. Throghout the series, we see examples of the malevolence behind her zen-like fascade, such as when she impersonates Kira, leads the Dominion occupation of Deep Space Nine, and orders the slaughter of the Cardassians at the end of season 7.
Gabrielle from Xena also counts as an extreme version of this in mid to late Season 5. Her bitchiness was so noticeable, out-of-character and unpopular, that it was actually lampshaded by Gabrielle herself in the episode "Eternal Bonds".
Gabrielle: ... I can be a real bitch sometimes, can't I?
Also, taken Up to Eleven by Varia. In every appearance she ever had, Varia was at first made out to be friendly, and as each episode panned out, she became the bitch yet again. Taken up again by yet another eleven by Varia in "To Helicon and Back", which featured Varia selling Gabrielle out to a genocidal maniac, bent on the destruction of her people. Nice.
Velasca wasn't very good at playing the sheep, but she also counts as this.
Amarice in her first appearance was similar to Velasca, but was also more of a Well-Intentioned Extremist, even trying to take on Xena, in her attempted protection of Gabrielle in "Endgame".
Ephiny inverts this trope in her first appearance by being aggressive, unfriendly, and cold toward Xena and Gabrielle, before eventually becoming one of their best, and most trusted friends for the rest of her life.
Jasmine from Angel has a hypnotic power that causes everyone who sees her to instantly become entranced and view her as perfect and beautiful, which hides the fact that her true appearance is of a decaying maggot-covered corpse, and she eats people. A lot. And wants to enslave the Earth. More to the point of the trope, while she acts like a wise and all-loving goddess when she's getting her way, an awful temper and vindictiveness lie beneath.
Cordelia, in the first episode. She's very kind to Buffy and looks out for her on the first day, but Buffy sees her for what she is when she insults Willow for her admittedly hideous outfit. Cordy eventually redeems herself in both Buffy and Angel, but can still pull out the bitch card when needed as seen in "Rm w/a Vu"
Whereas, by Season 7, one suspects that the reason Buffy spends every single scene with Spike is because no one else can stand her anymore. This is to the extent that the Scoobies and the Potentials get fed up with her bossiness, as well as having doubts over both her leadership skills and methods, and finally decide that Faith would be a better leader and kick her out.
The potential Slayers pick Faith over her. Faith. What's that tell you?
Willow can be this occasionally, especially in season 6.
Speaking of Willow, Lily in How I Met Your Mother. She's manipulative and controlling and very rarely takes other peoples' feelings or opinions into account, but never gets called out on it. She appears to be the sweet, maternal member of the group but is revealed at one point to have been quietly manipulating her friends' lives and relationships for YEARS (going back to before the show began).
Elliot Reid is this in most, if not all, of her relationships.
In an episode of iCarly, Carly meets up with an old friend named Missy, but Sam has suspicions that Missy is trying to get her out of the picture, but Carly believes otherwise. It turns out that Sam was right all along, and after winning a chance to take a cruise, Missy confesses to Sam about her intentions, but Carly was within ear-shot at the time, and it also turns out that Freddie won the cruise and gave it to Missy, who is actually prone to seasickness.
Marcy from Married... with Children, who is often presented as being old fashioned and loving of her husband Steve (and later Jefferson). However, she often ends up in situations where someone has wronged her, and this often causes her to describe in violent detail how she is going to exact revenge on them. In a similar fashion, she's also shown to be sex-obsessed, but she tries to keep this persona hidden from the Bundys, because she wants to look wholesome and be the voice of reason. It never works.
Dre from Noah's Arc. It takes a full season for the bitchiness to reveal itself, but when it does...
Sherry Palmer from 24 could've been the trope-namer.
In all fairness, she did get a Pet the Dog moment by helping Jack stop Peter Kingsley
Isabella from Robin Hood shows her true colors when she tries to kill Robin after he dumps her. However, it is unintentionally subverted considering Robin's questionable behaviour in this particular season, and the fact that it is heavily hinted that Isabella has mental problems thanks to seventeen years of an abusive marriage. Likewise, the Derailing Love Interests trope played a part, as Robin hooked up with Kate soon afterwards.
Kate herself was petty, mean, jealous, spiteful, and vindictive...not that the writers ever noticed, considering she was an almost too-perfect example of a Jerk Sue masquerading as a Designated Hero.
One of Rachel's boyfriends (played by Ben Stiller) in season 3. He seems perfectly fine until someone or something pisses him off. Also Joey's first new roommate Janine who hate Chandler & Monica.
Emily, Ross's 2nd ex-wife. Later on in her appearance, she became much more...not bitch per say, more along the lines of 'possessive extremist with a short temper'. Granted, she had reason for being not so innocent anymore (Ross said the wrong name at the wedding), but her 'demands' were admittedly quite unreasonable...
Rachel also comes across like this, frequently manipulating Ross's girlfriends behind his back, forcing him to take all responsibility for their relationship problems and drawing all attention to herself.
Phoebe, late in the series, especially in that episode where she and Monica try to break up and fire, respectively, a guy, but the first one to do so is the bitch. Monica rehires him but Phoebe doesn't take him back. She's also pretty horrible to Ross and Chandler (Monica's boyfriend and later husband) including introducing Monica to her "soulmate" while being well aware of Chandler's rampant insecurities.
Amy Pond from Doctor Who is something of an unintentional example. On the surface, she seems fun to be around, but she treats her boyfriend like crap. She does get better, but trying to seduce the Doctor the night before her wedding day, and attempting to kiss him on the day, was still a bit of a dick move.
It should be noted that, while she keeps bullying her husband for the whole series, later episodes make clear that she deeply loves him, to the point of not envisioning life without him.
We get something of an inversion with Donna Noble. She starts out as a loud, shrill harpy, but as time goes on, we realize that her attitude comes from her feelings of total worthlessness. The Doctor said it the best, "Shouting at the world 'cos no-one's listening."
In the Korean Series49 Days, In-Jung is the best friend of a girl in a coma. Come to find out, she set up the hostile takeover of her friend's company two years before the beginning of the story, using her boyfriend/lover as bait.
Patty Hewes seems to be invited to guest at a heck of a lot of morning news-and-chat shows in spite of her numerous nefarious, under-the-table deeds.
On 90210, Naomi's older sister Jen seemed like she truly cared about Naomi in her first appearance. Right until we learn that she slept with Ethan while he and Naomi were together (she would later go on to sleep with Liam while he was dating Naomi and blame Annie for it).
Annie and Dixon's cousin, Emily, seemed like a sweet, innocent girl who looked up to Annie at first. Then, she turned all of Annie's friends against her, tried to steal Liam away from her, and got Annie fired from her internship and suspended from school...all while pulling the Wounded Gazelle Gambit.
Marisol from Degrassi is cute and cheerful (if a bit dim), however, she flirted with, and possibly had an affair with, KC while he was living with his girlfriend and son, and told the entire school that her childhood best friend Katie was a recovering bulimic, almost causing Katie to relapse, all because Katie was dating Drew, who Marisol went on one date with months ago.
HRH The Princess Eleanor from The Palace charms the public with her poise and charitable endeavours, but she's really a ruthless schemer who will abuse anyone's trust to get to the throne.
Morgana from Merlin has fallen into this, mostly in the earlier seasons when she was pretending to be the good girl princess-her temper and strong will showed up from time to time, but Uther never knew she was as bad as she was. And she's openly evil nowadays. She wasn't really pretending to be good in the earlier seasons, she genuinely was kind-hearted, yet fiery when she needed to be. Since learning she had magic and resenting how magic-users are treated in Camelot, she turned against her old friends and became the evil villain she is now. Although, after turning to darkness, she did admittedly pretend to still be an ally of Camelot for a while, before dropping the ruse.
In Oz, Schillinger offers to be Beecher's new cellmate to seemingly protect him from Adebisi. Beecher accepts the offer from the seemingly helpful Schillinger, but on their first night in the cell together Schillinger rapes Beecher and "brands" him by burning a swastika design into his right buttock.
And let's hear it for Grace Whitney of Dance Academy: first she gets thrown out of the Royal Academy for driving another girl into a nervous breakdown; then she sets up Abigail (the only one who's even remotely onto her) as a villain to isolate her from her tentative friends Kat and Tara while also putting the moves on Abigail's choreographer Ethan and claiming he jumped her; she shows her true colours as a shameless and manipulative liar while rehearsing a 'self-revelation' choreography assignment, but still manages to convince everyone that she's a total sweetheart and 'the least competitive girl at the Academy'. Don't you believe it. Grace will do anything to get ahead.
Victorious had a girl named Ponnie, who pretends to be innocent and befriend Tori, but drives Tori insane because she claimed the moment Tori enrolled, Ponnie got kicked out. This is proven by Sikowitz to be untrue, but Ponnie still wrecks havoc.
The Big Bang Theory has Emily, Penny's friend from a common yoga class. Feeling bad for Raj, unable to hold a girlfriend due to his embarrassing selective mutism towards girls, Penny and Howard try to hook him up with a sympathetic, funny and likeable deaf girl. While the plan seems to be successful, Emily soon reveals to be much less cute and lovingly as she seemed to be, pestering Raj for expensive gift and a lavish lifestyle, ultimately turning against him when her plan is discovered and Raj proposes her to live a more conservative lifestyle from then on.
On the show's main trope page, Raj's sister, Priya, is implied to be one as well.
Person of Interest: When we see Root in the season finale, she plays the part of a meek therapist who is being hunted down, giving no evidence of her true nature until we see her shoot a woman from behind and hold Finch up at gunpoint.
"Your grace is wasted in your face. Your boldness stands alone among the wreck."
By Word of Goddess, Sara Bareilles considers herself one of these. She's said at more than a few interviews that she finds it very amusing that she can fill her albums with angry songs that chew people out or tell people off, and people turn around and love her for it. In her words, "You can be a total bitch, but if you say it in a happy, peppy, sweet way, absolutely no one will notice."
The titular Christine in "Devil in Disguise (Chrstine's Tune)" by The Flying Burrito Brothers is made out to be one.
"Down At The End Of Your Road" by Jethro Tull, a Broadsword And The Beast era song describing a man who, by day, is a well respected real estate businessman, yet, by night, is a Jerk Ass who messes with the neighbors in various ways.
From Greek Mythology, Hera in pretty much all depictions. Queen of the Gods! Goddess of Marriage! Nice woman, right? Wrong.
Aphrodite is actually a better candidate. Arguably the Ur Example of the Brainless Beauty, and seemingly too innocent to perpetrate a single evil act. But she regularly runs the gamut from petty and mean to pure evil.
Grimhild in Norse Mythology. She made Sigurd forget about Brynhildr so that her own daughter Gudrun could marry Sigurd. This ends up getting both Brynhildr, Sigurd, Sigurd and Gudrun's son and Grimhild's youngest son killed. Then she forces her daughter to marry Brynhildr's brother despite that he may want to take kill Gudrun's brothers in revenge. Grimhild herself gets away.
In For Better or for Worse, when Elly is interviewing a replacement for Kourtney, she thinks the candidate seems like a nice person from her application, and wonders why she was let go. She calls up, and the woman on the other end seems polite up until she screams at her child for acting out. Elly politely removes her from consideration, having heard all she needs to.
In Exalted, the Black Claw Style of Supernatural Martial Arts is based entirely around this concept; most of the techniques of the style are variations on the Wounded Gazelle Gambit, and the final Charm in the style is a powerful attack that becomes unblockable, undodgeable, and even more powerful if its target is someone who genuinely loves the user of the style.
Dimentio from Super Paper Mario is a polite, almost perpetually-smiling court jester who pretends to be on the side of the heroes. Then, he tries to destroy reality.
Mimi also fits this trope, although she drops the "nice" facade within a few minutes of meeting Mario (when he breaks her vase). The player knows she's evil from the get go, though, and she pulls a Heel-Face Turn at the end.
And in Paper Mario: The Thousand-Year Door, there's Grubba, who acts nice to Mario for most of the chapter, but turns out to be a total bastard who's been using the chapter's MacGuffin to drain the life energy out of people later.
Nur-Ab-Sal from Indiana Jones and the Fate of Atlantis is the spirit of an Atlantian king who Sophia claims as her spirit guide. Indy, as a scientist and a cynic, is less inclined to buy into the mumbo-jumbo of the spirit world... though, through his guidance of Sophia and various displays, Nur-Ab-Sal proves to be quite real on more than one occasion... Real, really controlling, and really bad news. You initially think that Sophia is just protective of her necklace because she refuses to trade it or remove it, but gradually, with the right dialogue—especially in the team version—you realize that it's Nur-Ab-Sal who's possessive of Sophia. Upon reaching his "throne room" in Atlantis, he finally fully reveals his true colors by possessing her completely, claiming to Indy that the time for human frailty has passed, and dooming her to die there as his vessel.
Many characters in the Ace Attorney games are like this, and they're usually the true culprit of the crime.
Apollo Justice also had Alita Tiala, a seemingly loving, devoted fiancée to Wocky, the defendant of Case 2, who was, in fact, marrying him because she and the victim of the case were the only two people who knew that Wocky was going to be dead soon. In fact, she carried out the murder to prevent being ratted out, and blamed it on Wocky.
Matt Engarde is a pretty decent male example.
As is Kristoph Gavin.
Subverted in T&T case 2, where everyone expects this of Desiree, but she's genuinely a nice person.
And deliberately invoked in Investigations. Colias Palaeno was designed to be as friendly and sweet as possible to make veteran players suspect him right off the bat. In fact, he's exactly who he presents himself to be, and was just Manny Coachen's pawn.
Halo's Prophet of Truth comes across as polite and affable at first to the Covenant, until it's shown that he tried to commit Genocide against the Elites, and he becomes hysterical by the end of Halo 3.
Atris, from the second Knights of the Old Republic. She even wears white. Despite her crappy attitude, she presents herself as very much holier than thou; the quintessential perfect goody-two-shoes Jedi. In reality, she has turned to the dark side and caused countless innocent deaths. Executive Meddling caused the extent of her evil acts (causing the destruction of Katarr, the extinction of the Miraluka, and the death of hundreds of Jedi just because she loved and hated the Exile) to be cut from the finished game. If anything, she's a unique case in that she has no idea how bad she was until she's shown.
In the beginning of Dragon Age: Origins, Queen Anora seems like nothing but eye candy for King Cailan, and, after his death, became the justification why her father should be the regent in the absence of a king. Towards the end of the game, you have to rescue her from a castle where she is kept against her will by her father. Once you have saved her, it turns out that she had been running the kingdom all the time. That her father arranged for the death of her husband seems not to be bothering her too much, but she isn't going to let him take away her kingdom. She agrees to marry her late husband's half-brother to strengthen her claim as the queen, but only under the condition that she keeps running the show and he is going to be only for show.
Sister Petrice plays one in Dragon Age II as she manipulates events in order to start a war with the Qunari.
Aerie comes across as the sweet, innocent Woobie of the group for most of the story, but gods help anyone in a romantic rivalry with her. It's telling that Jaheira, whose status as a short-tempered Tsundere is the stuff of legend, has the clear moral high ground when the two of them fight over a male player character.
Borderline example: Rin Tohsaka from Fate/stay night, who combines this with Jerk with a Heart of Gold. She's not a bad person, but she's Cool, Dark and Snarky, rather than the "perfect honour student" image she shows to the rest of the school. The only ones in on her in on her real personality (barring Shirou, who's a bit traumatised when he finds out) are her rival Ayako, who has a similar facade going on, and Issei, who served with her on the student council in middle-school and got to see her true, pragmatically ruthless nature. Sakura seems to have at least some idea too, because she's her sister. She has rather mixed feelings, however, since she worries about what Rin might do to Shirou in the war, but at the same time, clearly still loves Rin, and desperately wants to be acknowledged by her. How much of this you see depends on the route. In Fate, you see some of her kindness amongst her glorious snarkiness. In Unlimited Blade Works, her kindness is fully displayed. In Heaven's Feel, she seems to drop the 'heart of gold' entirely and just becomes a bitch — especially towards her sister, Sakura — until the end of the final fight, where she demonstrates that her bitchiness had really been a facade all along, as an attempt to persuade herself that she could, after all, killSakura if she had to. The True End of the Heaven's Feel route implies that she has dropped the "bitch" part entirely, at least as far as Sakura and Shirou are concerned.
Athena in the God of War series. She plays The Obi-Wan role for most of the first game, and in the third, though posthumously, only to reveal her true nature after Zeus is killed. When Kratos sacrifices himself to release Hope to all of humanity, Athena wails, "You fool! That was supposed to go to me! The mortals won't know what to do with it!"
Actually it's implied that this was God of War III only. The box's evils infected the others so it may have influenced her as well. She also states that becoming a ghost caused her to "see the bigger picture" so it's quite possible that she only fell prey after death and may have genuinely cared about him in games one and two. Hell Zeus himself flat out states she refused to betray him.
Adachi Tohru in Persona 4, in the Normal/True playthrough.
Izanami might be a more subtle example. She's a goddess who gives people incredible power and sits back as two of them endanger the lives of innocent people, and ultimately ends up trying to kill you. Her disguise? An androgynous, and relatively friendly gas station attendant.
Scott Selby in Heavy Rain. At first he comes across as a nice, compassionate guy, who even rescues a suicidal mother and looks after her baby, but is actually the Origami Killer.
Fal from Symphonic Rain who only acts nice to the protagonist in order to take advantage of his musical talents.
Paz from Metal Gear Solid: Peace Walker. She introduces herself as a sweet college student longing for peace in her beloved country, Costa Rica. Even after knowing that her "professor" works for the KGB, Snake decides to accept the mission just for the sake of this girl, because he thought that her feelings were genuine. But then she turns out to be the game's final boss when she steals YOUR beloved Metal Gear ZEKE, pilot the damn thing in her underwear, and tries to blast you with a railgun. She actually works as triple agent for the KGB, CIA, and mostly Cipher the proto-PATRIOT. Thank God Snake then blows her ass out of the Metal Gear, into the ocean.
Her actions also serve as a testament to how far Zero and the Patriots have fallen in the past ten years, as its revealed that she was scared to death of failing them and considered inciting their wrath a Fate Worse than Death; indeed, her diaries reveal that she actually Became The Mask to an extent and wished she didn't have to do what she did.
Given the lighthearted nature of the series, Pamela from Atelier is a Played for Laughs case. Well, she's not evil, but some things she does are not very...nice.
In Trinity Universe, she more or less states that she does those things only because that's how ghosts are supposed to behave. She genuinely is dense to the point that she doesn't realize what she does can be construed as 'evil', and all she really wants is a friend to play pranks on. Even when she goes ubercreepy and helpfully hopes you'll die soon, it's only because she thinks that way you can have fun being ghosts together with her.
Levin, aka the third World Eater Raksha, from Soul Nomad & the World Eaters combines this with Obfuscating Stupidity and spends most of the game pretending to be a good-natured goofy moron. Disturbingly enough, while he isn't good-natured or moronic in the slightest, he still comes across as a little goofy when Trish confronts him. This is also one of the rare cases where, depending on Relationship Values, the person in sheep's clothing can end up Becoming the Mask.
Dragon Quest IX has Mayor Bryce, who runs the struggling Port Llaffan. While he treats Jona kindly, acting like a surrogate father for the recently orphaned girl, he's mainly interested in abusing her ability to summon the great whale, Leviathan. When she says that she's not comfortable overusing that power, he immediately replies, "Well, it's not like you can do anything else for us, useless girl." It's not simply a matter of helping their village survive, either; he keeps her summoning to the point where everyone completely abandons their fishing as useless. And even before she developed her power, when they were honestly struggling to survive, he still wouldn't let anyone else use his private fishing hole...better described as an entire coastline.
Randy from Valkyria Chronicles II qualifies. He's the ideal student council president, comforting those who are down and out and helping old ladies across the street. And then you bring him into battle...BANG BANG BANG PLOP. "How unfortunate." The whole nice guy thing was just a facade so that he could set himself up for a leadership role. God help you if he perceives you as a threat to his role as a leader and the center of attention.
Tokimi in Eien no Aselia. Only Yuuto ever seems to realize it. Deep down, she's really not so bad, though.
In World of Warcraft Cataclysm, it turns out that Hope Saldean, the kindly adopted daughter of the Saldean farmers who cares for the people of Westfall, is actually Vanessa VanCleef, who seeks to revive the Defias Brotherhood and avenge her father's death.
Captain Shannon from The Orion Conspiracy. He seems to be a nice guy, giving a eulogy to Danny, Devlin's son, and letting Devlin say something at the funeral. He seems to care very much about the crew (notwithstanding some hostilities between him and the engineer Meyer), and is a little condescending towards Devlin, on the grounds that Devlin is middle-aged and Shannon is in his prime. Shannon also seems to be rather anal about the rules. Then, when Kaufmann is murdered, Shannon blames Devlin for the murder, ignores Devlin's protests of innocence, has Devlin imprisoned, and decides to cover up the murder, keeping it between himself, LaPaz, and Ward. So you would think, what a sleazy guy, right? Then Devlin and Shannon have a confrontation later on and it is revealed that Shannon blames Devlin for the death of Shannon's wife, so he murdered Danny as part of his revenge, then he murdered Kaufmann to frame Devlin, and now he is going to murder Devlin. Now that is a Bastard In Sheep's Clothing! Good thing Meyer intervened before anything else happened.
Harvestasha in the sequel, very Moe in an appearance and has a very squishy voice, but doesn't hesitate in disabling her trusted friend in an attempt to wake up a Physical God.
James Tobin from In the 1st Degree. He seems like a nice guy who got caught in a bad situation at first. However, it will become clear that this is only the image he is trying to project, as he is trying to not be found guilty of murder and grand theft. Luckily, he is not very good at projecting this image. In fact, if you play the game right, you'll be able to make him lose his cool completely, and then he will show himself for what he is right in front of everybody in the courtroom.
Jeannie May in Fallout: New Vegas, who gets found out during a quest to find out who sold Boone's wife to Legion slavers to have her lead out to be assassinated in front of the local tourist attraction, later, and nothing of value was lost.
Tingle is perky, cheerful, and near-sycophantic when talking to Link, but if you talk to the guy in pink, he reveals that he's Tingle's younger brother, and Tingle is incredibly abusive, but on days when you visit, he's so much nicer (he does not, however, specify if "so much nicer" is enough of an improvement for Tingle's behavior to qualify as "nice" on its own)! If you talk to the guy in white, you find out he's not even related to Tingle; he's just some poor schmuck who happens to look like Tingle, and washed ashore one day after a boating accident, and Tingle has been forcing him to do menial labor ever since.
In Disciples2, Uther first appears as The Chosen One who will save the Empire from ruin. The first hint that he's not the Messianic Archetype is the way he cruelly mocks the Dwarven King's grief over his lost son. During his coronation, Uther drops all pretense by murdering his father the Emperor with hellfire and summoning demons in the heart of the capital. He then reveals his true demonic form and his goal: to conquer Hell itself.
The Witch's House, Ellen, especially in Viola's body. She used Viola to get her body, tortured her by having her legs cut off and eyes gouged out and gave a powder to hurt her further, killed a frog after it helped her and its tadpoles, and, worse of all, laughed at Viola after her own father killed her/
Maya Brooks, the goofy, jovial, friendly Alliance Staff Analyst from the Citadel DLC for Mass Effect 3, as it turns out, was an ex-Cerberus officer who left the group out of disgust because the Illusive Man had started looking to non-humans for help. She also was the one who orchestrated the mercenary ambush in the Wards to intercept Shepard's Spectre code and the one who killed Khan. She was working with Shepard's clone in an attempt to steal Shepard's identity, and, after leading Shepard and their party into a trap, leaves them to suffocate to death in an iridium vault. At the end of the DLC, she shows that she doesn't even have any loyalty to Shepard's clone, as she leaves them to their death as well. She at first appears to be one of the nicest characters in the series, but ends up being one of it's most heinous.
Chiaki in Our Two Bedroom Story is described as "gentlemanly" and having a "sweet face," and he exerts himself to come across as pleasant and cheerful to his co-workers. However, as the protagonist soon discovers, his true self is something less pleasant - though not unredeemably so, given that he's one of the possible love interests of the game.
To first time players of Super Dangan Ronpa 2, Hiyoko Saionji's child like appearance and attitude during her introduction would most likely come off as adorable and some would even think she's going to be a sweetheart. That thought is ultimately crushed only seconds later when she reveals that she's laughing because she's playing with ants and likes the "pop" noise that happens when you crush them, and then snickers evilly and calls you a "Coward" when you refuse to join her. Her personality and habits just get worse from there, but her cute appearance never changes.
Felicia from Ozy and Millie, literally. She's the school bitch, and she's a sheep.
In The Gamers Alliance, Desdemona and Vaetris seem genuinely nice and likable people but underneath that kind exterior they're anything but. The former is actually a power-hungry, backstabbing schemer who killed one of the heroes and is currently manipulating King Marcus into marrying her in order to subtly take over the Remonian throne, and the latter is one of the four dreaded archdemons in disguise whose goal is to keep other races divided so that she can take over the world with her demon horde.
In the Travel Channel website-original animation "Anthony Bourdain's Alternative Universe", we see a fictional side of travel hostess Samantha Brown we don't normally see on the air, in the episode "Romanian Rhapsody" (Sam's segment starts at the 1:40 mark). Seeing the burned corpse of the fictional Anthony Bourdain, she goes, "Yeah, NOW who's laughing, funny man?" Sam kicks the head off the body, then gets an evil look on her face as she goes, "Guess that 10:00 time slot just. became. AVAILABLE." Spouting off to a nearby camera man, she tells him when she's calmer, "Go get the head and send it to Rachael. She'll appreciate it." One final rant, and then she gets the clapboard in front of her face. Once the clapper comes down, she's her normal smiling self again.
Survival of the Fittest v4 has Aaron Hughes as a male example. He starts out wanting to start an escape plot, but throughout the game, he manipulate every single character he comes across, and eventually decides to play the game conventionally while still keeping the guise of the leader in an escape plot. Ashlie Jackson of Evolution is also hinted to have been one of these before being put in the experiments, and although her power rendered her unable to pull it off as much, she attempts to pull off a Cute Mute facade at one point. And as early as his first appearance, Simon Leroy of Virtua is already shaping up to be a male example, who started out the game attempting to get Sycanus Appletin's trust by pretending to be a Nice Guy...while planning to use her trust to his advantage.
Solange of the Whateley Universe started out this way. As a frosh, she was kind and understanding to Montana even though he looked like a sasquatch... and then she publicly humiliated him. All so she could force her way into the top clique of the school.
Esmeralda on The War Comms is a variation; rather than everyone thinking she was gentle and sweet they thought she was too passive and whiny to do any real damage. The "sweet and proper lady" image was her own insistence, even as her claws started coming out...and then this happened.
Suzy Johnson on Phineas and Ferb, though possibly only when it comes to girls her older brother Jeremy likes (and whom she thus feels are a threat to her status as his "favorite girl").
Apparently, she also torments Buford, but the audience has never seen her do it.
Subverted in The Fairly OddParents, where Timmy summons a pop star for his babysitter to forcibly marry, expecting that he will be an example of this trope...however, he turns out to be a very nice and easygoing guy.
Vicky in the eyes of Timmy's parents, usually.
On Futurama, Leela dates the Mayor's Aide, and he pulls strings to get her nice perks, before discovering that he was a creep who deprives orphans of fun and commits other such selfish acts to get those perks.
Also Mom, the grandmotherly industrialist who is secretly a bitter, old hag.
And Zapp Brannigan, of course. The Zapp Brannigan!
Then again, it has more to do with just about everyone's inability to recognize Zapp's incompetence.
Also Professor Farnsworth. Considering that some of the less disruptive things he's done in the show include creating albino atomic apes for the sole purpose of proclaiming his love for Mom, and the implication that he has multiple doomsday devices, his charming and harmless-seeming senility could be just a very good act.
Lois in Family Guy definitely falls here in the episodes where David Zuckerman isn't involved. Granted, she is a sensible person and the usual voice of reason, but really get her going and she can do some rather questionable things and not bat an eyelash. Can't even get the courage up to say "I Love You" to her daughter Meg (she merely mumbles it) on her wedding day, no less.
Even lampshaded in one episode where she is described as "more of a bitch than she lets on."
Goes even further in the 'Foxy Lady' episode when Peter draws Red Heinie Monkey's female sidekick "who's always nagging at Red Heinie Monkey and telling him not to leave his beer cans lying around and what not."
Peter: [Holding up a drawn picture of Lois with a duck bill instead of a mouth and nose] And her name is Bitch-Duck.
Meg: That kind of looks like Mom.
Peter: Not finished talking, Meg!
Most formerly pleasant characters or Straight Man types have gained extreme Jerk Ass traits that makes them into this trope. The frequent Comedic Sociopathy in the show has arguably lent to the more openly Jerk Ass characters, like Stewie, actually having more genuine redeeming aspects than the designated "nice" ones, such as Lois.
The undoubtedly overly sweet New Brian bonded with the family so well that he seemed to be a perfect replacement for Brian until Stewie found out something incredibly dark about New Brian; the dog humped Stewie's teddy bear, Rupert, and New Brian rubs salt in the wound by saying that every time Stewie holds Rupert, the bear will think of New Brian instead (and this is complete with a smug grin). Stewie proceeds to kill him.
Bonnie counts here as well. In "Go Stewie Go" she admitted to Lois that she cheated on Joe before, and encouraged her to do so as well instead of talking to Peter about how him calling Lois old was hurting her feelings. She attempted to cheat on Joe again in "Foreign Affairs", but was stopped by Lois bringing Joe there to stop her. Then she acts like such a betrayed victim when, after acting cold and indifferent to Joe, he cheats on her. And in "And I'm Joyce Kinney" when Joyce Kinney reveals in her news broadcast that Lois had done a porno, Bonnie immediately runs over to the Griffin house to point at Lois and call her a slut.
When Chris dates a girl with Down Syndrome, she appears to be nice, but Chris finds out later on that she's a controlling and stuck up bitch that expects her date to do everything for her. Chris finally snaps and calls her out on it.
Ferris Boyle from Batman: The Animated Series. While he pretends to be a humanitarian, he is really a callous monster who cares only about money. Even Batman, who's usually pretty stoic, is horrified to the point of even muttering an audible "My God!" (an EXTREME rarity in cartoons in those days), when he discovers the full extent of what Boyle did. The only happy part in the whole episode is knowing that Boyle will face justice for his crimes thanks to Batman.
Quite a few characters on The Venture Bros. can be this from time-to-time, but nobody takes the cake like Dr. Jonas Venture. When the show started, he was just shown as a God-like super-scientist and globetrotting adventurer who was just plain better than his son and heir, Rusty. But as the show went on, it was revealed that he was an extreme Jerkass who went back and forth between neglecting his son and putting him in situations of traumatizingly-high levels of danger. Further, the reason Rusty is such a failure who can't live up to his dad is because of his horrible upbringing which has left him a mental wreck.
Rusty's brother Jonas Venture, Jr. seemed like a nearly-perfect human being when he first emerged from Rusty's body. Only gradually was he revealed as a lousy husband and all-around self-involved jerk.
In Codename: Kids Next Door, Numbuh 3's little sister Mushi, at first, comes across as being just as childish and ditzy as her older sister. However, when she is stuck alone on the space ship with Cree and Numbuh 5, she gives a speech about how they should stop fighting because sisters are supposed to care about each other and be friends. As the teenage villain stops to think about this, the little girl pushes her out of the airlock, turns to Abby, and says "older sisters always fall for that mushy stuff". In her next appearance, her true colors are revealed as she stabs her sister's stuffed animal and is sent to her room forever. After that, she becomes a full-fledged villain and creates a spanking monster to attack kids.
Hama in Avatar: The Last Airbender is one of the creepiest examples. When first met by the protagonists, she appears as a sweet old lady with a sympathetic backstory and a mentor to Katara. It eventually turns out she is a crazy sadistic woman who created the ability of Bloodbending and let her obsession with revenge toward the Fire Nation overcame her, causing her to kidnap and sequestrate Fire Nation civilians.
Darcy from Winx Club does this in one episode. After seemingly saving Riven's life, she deliberately acts sweet and cutesy (she even says "My name's Darcy" while giving a big cutesy smile that make her two psychopathic sisters disgusted). Next episode, she's back to being a seductive and evil bitch who attempts to commit homicide against her rival for Riven (which shows how spiteful she is, given that she didn't even like Riven, and yet still wants to murder Musa just for liking him. Jesus).
Invader Zim: Tak from the episode "Tak the Hideous New Girl".
Pietro in X-Men: Evolution is introduced as one. At first, he pretends to be nothing more than a Rival, and even helps Evan in luring a trap against whoever's ripping him off. Then he reveals, in an awesome manner, that he is the one who's been messing with him, and leaves him framed for vandalism and theft.
Kitty accuses Lance of this at the beginning of Season 3.
The show also has a more extreme example in the form of Chrysalis from Canterlot Wedding.She disguises herself as Shining Armor's bride Cadence; just to harness his love for her as energy for her Changeling invasion of Canterlot; and imprisons the actual Cadence in the caves beneath Canterlot that most ponies had forgotten even exist. When Shining Armor's sister Twilight, having seen fake Cadence casting spells on Shining Armor, voices her own suspicions, fake Cadence plays innocent and makes it look like Twilight's only accusing her out of possessiveness of her brother. Fake Cadence then imprisons Twilight in the caves beneath Canterlot, away from the actual Cadence hoping neither will find the other.
What inverts this trope is Fake!Cadence didn't really attempt to hide being a bitch at all except for when Twilight attempts to accuse her of being evil. The closest she did otherwise was when she said Applejack's treats for the wedding were okay and then proceeded to secretly throw them all out, but all other times she snapped at or insulted everypony she came across. The other members of the Mane 6 just didn't really pay that much attention to her behavior, or believed it was justified what with the pressure of the wedding coming up. The reason Twilight was suspicious in the first place was because the kind, sweet Cadence she knew from when she was still a filly behaved so radically different compared to now.
The Reverend Lovejoy's daughter Jessica in The Simpsons. Everyone believes that she's a sweet, innocent minister's daughter, but (much to Bart's dismay) she's actually a manipulative little bitch. At the end of the episode her father is revealed to be well aware of her hellish behaviour, but overlooks it (to the extent of covering his ears and singing hymns at the loudest pitch possible) and tries to pass the blame onto Bart instead. Given the addition of the Lovejoys' very fickle and conditional devotion to the bible and society, the Reverend and his gossipy wife may also count as this trope.
Qilby from Wakfu. He's practically unrecognizable the moment he ditches the Sheep's Clothing.
Hiroshi Sato from The Legend of Korra seems nice at first. Cue episode 7 when he reveals himself as the Evil Genius of the Equalists who hates Benders with a passion. His real thoughts concerning Mako and Asami's romance are absolutely vile, and he calls Mako a "fire-bending street rat."
Tarrlok also counts. He appears to be a politician who cares for the safety of the city, but that is just a cover for his real personality, a manipulative Jerkass that plays most of the heroes, getting one of them to resign to position, almost got them killed, and even went into darker territory by creating laws that discriminate against non-benders, even being cruel on enforcing them. He is vicious enough to where he doesn't need a full moon to bloodbend.
Li'l Gideon from Gravity Falls is an adorable child beloved by everyone. Just don't get on his bad side...
Barbie Mariposa has Henna, who is Mariposa's friend at first until she poisons the Queen and nearly kills all of the fairies in Flutterfield so she can take the throne.