Sexual attraction is a funny thing, and sometimes if a character physically appears to be the right gender to appeal to their sexual preference, then they'll become attracted to them, regardless of what that character's actual gender might be. Usually said character's true gender is being kept secret purposefully and they are a male Disguised in Drag or a female disguised as a male, but whether the misunderstanding was intentional or not, due to Rule of Drama, they will find out and it will be awkward, hilarious and possibly traumatizing for all involved.
This can happen to any gender and sexuality. A straight male might be shocked to find the girl he's been crushing on was a male all along. A straight female might be confused to realize that hot guy she's been daydreaming about was actually a woman. Her male Gay Best Friend, who was also daydreaming about the guy (who is really a girl) will probably feel similarly. Almost always there is shock upon The Reveal, possibly even some disgust, anger or disappointment on the part of the character who was feeling the attraction, but usually the two characters can reconcile by the end and become friends. Other times it might not bother them, or after a period of consideration, they'll decide If It's You, It's Okay.
This is both a reveal trope as well as a character reaction trope, when what initially appears to be compatible gender attraction is later revealed to actually be incompatible gender attraction (Example: Straight boy likes a girl, girl turns out to be a boy). It is a sister trope to the related Sweet on Polly Oliver, which refers to when what initially appears to be inexplicable incompatible gender attraction is later revealed to actually be compatible gender attraction (Example: Straight boy likes a boy, boy turns out to be a girl), although since the unsettling part is averted, this is usually a subversion (usually).
Note that in Real Life, this trope can have violent or even lethal consequences - there are numerous examples of people being physically or sexually assaulted when their "true" gender is revealed and some people have even been murdered.
Compare with Shapeshifting Squick, Dude Looks Like a Lady, Lady Looks Like a Dude, Bifauxnen, Gender Blender Name and Samus Is a Girl. Often accompanied by Attractive Bent Gender. Contrast Jumping the Gender Barrier and She's a Man in Japan. A subtrope of Gender Reveal.
Spoilered pronouns are by definition self-fulfilling, so don't bother doing that.
Shugo Chara!: Nadeshiko/Nagihiko, whose family has a long-standing tradition of making its boys dress, act, and, for all intents and purposes, be girls for about the first twelve years of their lives. He had to repress all boyish desires, no matter how slight, and was forbidden from revealing his true gender to anyone.
Juubei-Chan 2. Dropped on the audience and on Jiyu, who spent the entire series thinking this person was either chibi spirit Koinosuke or reincarnated baby Koinosuke... only for it to end up being Koinosuke's never-before-mentioned daughter who looks exactly like him.
School Rumble: Second Semester plays this straight at the end of the third episode. One of the characters present lampshades the moment beautifully.
"What... the hell?"
In The Secret Devil-chan: Kurosaki Sou, discovers this about Devil-chan, after just 10 pages into the manga.
Ship Leesoo finds out that the Bull is a female by kicking it in the groin to no avail. Justified because nobody could tell you that this◊ is a girl.
At one point, Italy calls Germany for help because "There was a pretty girl, so I hit on her, but it turns out the pretty girl was France in disguise!" Since France has a noticeable beard, one has to wonder how Italy made that mistake. Then again ...
And even more amusingly, fans that are new to the series often assume that the author of the comics is a woman. Imagine their surprise when they're told that Himaruya is a male and experience their own unsettling reveal!
This is a primary plot point in Blue Drop: Tenshitachi no Bokura. The main character must have sex on penalty of death with his best friend, who has been transformed into a girl by the evil lesbian aliens and impregnate him. Happens in the reverse, too; the friend in question is uncomfortable with having sex with the main character as well. Then it's found out that the best friend's mind was simply put over the top of a random alien girl's mind. When they fully merge at the end of the manga, it's unknown if he is a she with a guy's mind, or a guy still trapped in a girl body. It's rather messed up regardless.
Happens to a couple of Kuwabara's schoolmates at the end of YuYu Hakusho when they mistake Kurama for Kuwabara's pretty girlfriend. In the anime he's nonchalant and even jokes a little about it, but in the manga he gets homicidally angry.
Happens twice in the same minute in the anime. A dim bunch of henchmen have been told to apprehend a high-school-age boy, and they identify Fuko (a very tomboyish, macho girl) as their target. Immediately afterward, the rather feminine Tokiya screams at them, "You idiots! I bet you thought I was a girl!"
Subverted in the manga. Recca asks Aoi three questions, the third being "Are you a guy or a girl?". Aoi answers that he's a guy, but instead of being stupefied about the gender, Recca merely brushes it off to mean that he can fight as he pleases.
In an early episode of the R season, Mamoru and Usagi team up to take care of a baby named Manami whose mother is hospitalised after an attack from the Monster of the Week. When they change the baby's diapers, it turns out Manami is a boy and not a girl; he has a Gender Blender Name and had been referred to with gender-neutral pronouns. (The dubs generally handle it by referring to the baby as a girl first, and then as a boy.)
Happens in the anime Girls Bravo, where Fukuyama starts hitting on and eventually sticks his hand into the panties of a crossdressing Yukinari . His reaction is not pleasant considering the fact that he is extremely androphobic and is allergic to other men.
.hack - Given that the entire series is based on a fictional MMORPG, there are plenty of GIRLs around.
In .hack//SIGN, Tsukasa is the Bridget that gets dropped on herself. Among the initial worries that come with a revelation like this is that her gender will affect her relationship with Subaru. Turns out, it didn't matter.
It also happened in .hack//Roots when two female players attacked Haseo and their voices change.
The relatively obscure manga and animated movie They Were Eleven by Moto Hagio features an incredibly feminine recruit who is eventually revealed to be an alien who hasn't yet decided whether to be male or female, and actually became a recruit to avoid being forced to become a girl as well as a pawn in Arranged Marriage imposed by their family.
Poor Hayate gets forced into female clothing often, and there have been several cases of this. However, the most amusing was when he had to crossdress in order to attend an anime convention, and ends up having to fight a giant robot while wearing a maid costume. Naturally, this makes all the fanboys happy and taking pictures, even mentioning 'I saw white!' only to have Hayate respond that he's a guy. Their response? HE'S A TRAP! and, of course, take more pictures.
Luca, a pop star that Hayate helps after the robot hurts her, falls for it too, even going so far as to change in front of him. Due to the large amount of stress she's under, Hayate tries to keep up the disguise, digging deeper and deeper with lies. The plan finally fails when she gets into a bath that he's in, along with more than one of his female classmates.
One butler falls in love with Hayate, who at the moment is under a crossdressing curse (...). Although initially devastated when Hayate's cover is blown, he quickly comes around and tries to convince Hayate to travel with him to the Netherlands, where same-sex marriages are legal. (Cue Nagi's Megaton Kick.)
Ban and Ginji actually try peeping on the very girlish-looking Kazuki in a hot spring in an episode of Get Backers, mistaking him for a girl at a distance. Later, Amon Natsuki hits on him and tries to pull an I Kiss Your Hand. Juubei merrily skewers them both times.
Jan Suk in Monster has the Bridget to end all Bridgets dropped on him when he starts confiding in a cute blonde girl he met at a bar. Not only is she actually a man, but she's Johan. Also counts for the viewers, as it's a Shocking Swerve. Johan had been impersonating his twin sister as part of a plot to make her question her sanity, and his disguise and behavior were convincing enough that even the audience doesn't suspect the truth. The eventual reveal has caused anime clubs to riot.
During the Land of Waves Story Arc, Naruto meets Haku, whom he takes for a girl (Not thatthis ishard), and Haku corrected him on this assumption right before he left.
Haku: Oh, and by the way? I'm a boy. [goes away]
Naruto: No way?! He's prettier than Sakura!
Before the anime gave him a deep, masculine voice, Deidara was frequently mistaken as female.
Happened to Karin in Kamichama Karin at the end of volume 4 finding out her crush, Kirika-senpai, is female through an incident of seeing (and accidentally feeling) her revealed cleavage in an unconscious state. The audience gets the Bridget dropped on them first as it's revealed in an earlier chapter.
Shaman King has Amamiya Ryu aka Bokuto no Ryu, who thinks that Lyserg Diethel is a girl at first. When Lyserg reveals his gender, Ryu can't believe it until Lyserg either lets him check in his underwear (anime) or drops his pants in front of everyone (manga). Ryu doesn't seem to care and remains very protective and devoted to Lyserg even after Lyserg's Face Heel Turn and defection to the X-Laws.
Alto Saotome from Macross Frontier, a former Kabuki actor who often played female roles, gets this a lot... but trust us, he's certainly not happy about it. In one episode a salesman mistakes him for a girl and tries to sell him women's clothing, to which Alto angrily points at his Adam's apple and says "Does THIS look like a woman to you?!" Teammate Mikael loves to jerk Alto's chain by referring to him as "Princess Alto" and similar nicknames.
This happens to Riku Seya, a classmate of the Shuichi's older sister, Maho. Seya saw Shuuichi dressed as a girl and became infatuated, and convinced Maho to set them up. A future date at the aquarium turns into a rather shocking revelation which is not helped by a friend of Shuu's, "Mako-chan" (No, not that one) also revealing himself. Seya is left rather confused by it all.
The series has had a few instances of the rare female-to-male Transsexual case too.
In Rurouni Kenshin, Villainous Crossdresser Kamatari drops this on his opponent Misao (and everyone defending the Aoiya as well) quite dramatically, complete with pixellated naughty bits. Note that particular scene was only in the manga; in the anime he does reveal his gender too, but without flashing anything.
Kenshin himself often causes this with viewers, and the fact that he's voiced by a woman in the original Japanese makes it worse (and legend has it that the character designer for Guilty Gear first came up with the character Baiken after making this mistake) and he's in fact based on a historical samurai, Kawakami Gensai, who used his feminine appearance to get close to his targets and even managed to assassinate a man in broad daylight. He even hid out in a brothel at one point after an assassination.
Subverted in the adult manga Sundome; Sahana tells Hideo that she used to be a guy, but it's a trick to try to get him to stop masturbating so much. It Makes Sense in Context.
Happens to several characters when they discover Haruhi's real gender, most notably Tamaki, Kasanoda, and in the last chapter, the entire female customer base of the Host Club. And then Double Subverted when Haruhi tries to explain the truth of her sex to the club's customers, the girls assure her that they've known all along and don't mind a bit. Only later, after Haruhi and Tamaki have left for America, is it revealed that what they "knew all along" was that Haruhi was a gay crossdresser and that Tamaki was in love with "him."
Surprisingly does not happen with Haruhi's Drag Queen father Ranka. The host club knows that he's her father from the moment he enters the scene.
An oddly sexuality-inverted version occurs in Glass Fleet when Holy Emperor Vetti Sforza finally manages to get Michel Volban, the leader of La Résistance, into his clutches... and, upon drugging Michel in order to have his way with him, discovers that Michel is actually a woman. Vetti seems rather put out about it.
The reverse happens to Akane at the very beginning of the series. She wasn't exactly thrilled to find out that the shy and awkward girl she had just made friends with was actually a guy.
A subversion: Hiroshi and Daisuke's discovery that the cute redheaded girl they were hot for is actually their male best friend does absolutely nothing to stifle their crush ("Why can't there be more girls like him?")... though this is because Ranma doesn't wear bras and tends to get "her" shirt destroyed in public fairly often, as well as being willing to dress up in deliberately "sexy" clothes in order to manipulate Kunô or some other sap.
This happens to Ranma too, when he tries to romance Tsubasa to get "her" to give up on Ukyô and his own female side. His reaction to finding out Tsubasa is a maleMaster of Disguise (which includes crossdressing as a girl) is not pretty.
Everyone believes Konatsu to be the legendary Genius Kunôichi (female ninja), and have even braced themselves for her coming out of the closet to confess undying love for Ukyô. Then a stray bomb goes off, blows apart Konatsu's outfit, and reveals "she" is a very feminine-looking "he". Ukyô is just as stunned as everyone.
A rather bizarre example occurs in Fist of the North Star: Rei is introduced wearing a pink cloak and is mistaken for a woman, as only his eyes are visible. It's not until he speaks, and fully pulls the cloak off that his manly bod is revealed. It's worse in the anime, where Rei is pursued by several men trying to get a date.
In Gankutsuou, this happens to Albert as early as Episode 2. The "woman" then proceeds to tease him about it for the rest of the series. And later appears to go on to a successful modeling career... This is an expansion of a minor character from The Count of Monte-Cristo, who lured Albert into Vampa's trap.
The main premise of Stop!! Hibari-Kun! Main character Kohsaku moves in to his dead mother's yakuza friend and falls in love at first sight with the eldest and most beautiful of his four daughters... only to later find out that he is actually a very convincing crossdresser. Hilarity ensues.
Classic example: Shun from Here Is Greenwood. He's used for a prank because of this, and the reveal (more rage-inducing than unsettling) comes when he's caught in front of a urinal.
Happens to Greed in one OVA in which he flirts with "Winry" who is actually the shapeshifter Envy, who is male in this version.
Cowboy Bebop: Ed! Nobody finds out she's a girl until Faye tickles her! Everyone else can be forgiven since she's a pre-pubescent Tomboy with little social skill, and it's also a Mythology Gag to when Ed really was a boy in the original version of the story before being changed to a girl for cast balance.
A downplayed version-Gren is a male with female breasts due to being used for drug testing.
Happens once in +Anima, when a boy named Kevin falls in love with Husky, thinking he's a beautiful Mermaid Princess. Eventually, Husky tries to break the news him that he's really the 'Mermaid Princess' without overwhelming him, but ends up screaming it at Kevin before becoming human again. Kevin, is, to say the least, rather shocked that his Mermaid is Husky.
An episode of Kodocha has a subplot where one of Sana's friends develops a crush on an upperclassman tennis player. When she confesses her love, the object of her crush explains that she's a girl.
In the anime of Rose of Versailles, the Duke of Orleans tried to invoke this by having a very girlish and young-looking henchman impersonate Marie Antoinette, thus ruining the marriage to the Dauphin. It doesn't work, since Oscar manages to stop him and Marie shows up in time.
Also tends to happen fairly often that Oscar herself is mistaken for a gorgeous man, only for Oscar or someone in the known to clear the mistake and unsettle the poor woman. Note that this did nothing to stop the creation of a rather large all-female fan club for Oscar...
Lesbian variant: In the first OVA of El-Hazard, Makoto is forced to pose as the missing princess Fatora. Apparently, he pulls this off a little too well, because Fatora's lesbian lover Alielle climbs into bed with him. Her response basically boils down to: "Well, that's new... wait a minute... Oh, my God!" The episode ends with both of them screaming.
In The Alternative World, the real Fatora tries to return the favor to Alielle, but instead finds Alielle's very similar twin brother. "It just went... squish."
Prunus Girl: Logically, Maki "knows" that Aikawa is a guy, but he still can't help but be frequently embarrassed by Aikawa's antics (and occasionally be tempted to take up offers to personally verify gender). Meanwhile, his friend Kadoyama is hopeless over Aikawa, declaring "who cares as long as (s)he's cute!" and getting really worked up. A nameless herd of classmates seem to agree.
Mobile Suit Gundam 00: Tieria Erde, although his voice and personality help to only keep the viewer in the dark for parts of the first episode. Still, his girly looks and the fact that he wears a fuzzy pink sweater when not burninating the countryside in his Gundam cause enough of a double-take to fit him in here. To add to the confusion, the people making the show claimed Innovators have no sex. They actually, meant that they were androgynous. It was just badly translated and underwent Memetic Mutation before the correction came around.
He doesn't make it any easier in the 2nd season, when it's shown that when it's needed, he can really fill out a ballgown. Maybe Eiji gave him some tips...
In the Hideshi Hino short story Sailor Psycho, a girl is invited to the school idol's house to paint her portrait. She ends up discovering that the school idol is really a crossdressing boy with a school uniform fetish. The girl is killed when she freaks out and we find out that the idol's "mother" is really his crossdresser father and the old caretakers of their mansion are also crossdressers.
Subverted in The Day Of RevolutionFormer boy Megumi actually wants to drop a Bridget on the only boy at school who doesn't know her "secret" but the other girls forbid it for reasons of their own. (And when she finally did decide to tell him he wasn't listening.)
Played with in all directions in the manga series Family Compo. The main character moves into his aunt and uncle's place, and finds out that his aunt is really his uncle and his uncle is really his aunt. They're a transsexual couple.
In episode three of Kinos Journey, a Bridget was dropped on all the audience members who thought Kino was a boy. The ones who guessed right didn't hesitate to pat themselves on the back.
In Maria†Holic Kanako, the lesbian protagonist, meets the girl of her dreams in the form of the Mariya after transferring to all girls school. Later she walks in on Mariya changing and discovers his secret. She spends the rest of the series being relentlessly bullied by him into keeping his secret and suffering innumerable Stupid Sexy Flanders moments.
In the Arina Tanemura manga Gentleman's Alliance Cross (Shinshi Doumei Cross), the character Maora was so feminine in the first volume that even the staff who read it thought that he was a girl. His real gender wasn't revealed until the second volume.
Gold: Hi there miss. Isn't it lonely to do sightseeing by yourself? Wanna go for a cup of tea together? The name's Gold. I'm from New Bark Town. Bugsy: I...I'm Bugsy from Azalea Town. And... well... I'm a guy.
Another Bugsy example happened in Golden Boys, another GSC manga. When meeting Gold, Bugsy referred to himself as "... a bug keeper boy..." which provoked a "You're a boy?" from Gold. Nothing else was noted though.
In the anime, Brock wound up subverting this on one occasion. He knew something was wrong when a ridiculously Hot Scientistdidn't make him delusional. Turned out to be a man in disguise working for Team Magma. In a later episode, he identifies the same disguised man out of two otherwise indistinguishable Jennies by the same lack of a Raging Stiffie.
An example between Pokémon: Meowth and Ash's Oshawott both fall for a Purrloin. The expressions on their faces following the surprise revelation are priceless. The pairing name for this Purrloin/Meowth became, appropriately enough, Bridgetshipping.
Happened to Blade in NEEDLESS after rescuing a crossdressing Cruz.
Himemaru in Rappi Rangai. Despite being born male, he decided to become a kunôichi because he had the "prettiest face in the village," though Kisarabi claims it was because he didn't want to put himself through the hard training to become an actual male shinobi. In either case, he seduced Raizou in his introductory chapter, and even after his secret came out he continued making passes at him every so often.
The entire population of Tsukugeshima in "Moonlight Sonata" case was not only surprised that the island's only doctor Narumi Asai is the Villain of the Week, but also that "she" is a man.
Much later, Conan, Hakuba and Heiji realize that the "Detective of the South", Natsuki Koshimizu, is a Bifauxnen instead of a waifish boy. They only find out when she puts onher school uniform... a feminine seifuku instead of a male gakuran like the one Heiji has just put on. (OTOH the "Detective of the North", Junya Tokitsu, already knew and didn't tell them; in fact, he was surprised to learn that they didn't know about Natsuki's gender.)
And the reverse-drop happens again when Action Girl Sera Masumi appears. Conan, Ran and Sonoko don't find out that the handsome and devil-may-care boy that said Ran was "his type" and helped them resolve a case, was actually a Bifauxnen... until she appears in a female highschool uniform and transfers to the girls's class.
In manga chapter 830, it comes up again. Sera is such a Bifauxnen that even Kaitou Kid mistakes her as a boy. After having knocked her out and stripped her down to her boyish underwear and shirt to steal her clothes. Said person doesn't find out until Conan explais it to him, and when that happens a VERY upset Sera returns and kicks him to the face.
A mild version pops up in How I Became a Pokémon Card. Akira's and his best friend Akari are beginning junior high, and uniforms come into play. Akari has to wear the female uniform, which provokes Akira to mention how he didn't believe Akari really was a girl.
Inverted in Akahori Gedou Hour Rabuge episode 9, where the son of a businessman that Kaoruko is babysitting (the kid, not the businessman) ends up being a girl, much to Kaoruko's dismay.
This happens to Wataru Takatsuki in Yubisaki Milk Tea in recent chapters. However, despite Yoshinori Ikeda's initial beliefs to the contrary, Wataru actually likes him even more.
Her in-canon introduction involved this trope, along with her new co-workers' reaction to the reveal.
She invokes the trope deliberately in an episode of the anime, when she gets a marriage proposal from an Idol Singer that she's not interested in. Aoi asks for a meeting and shows up in male clothes, telling him about her issues. The guy respects Aoi's wish, withdraws the proposal, and they decide to stay friends.
Cobraja ends up choosing Itsuki to be a Desertian (mostly) because he thinks she's a beautiful man. Then when Itsuki-as-a-Desertian swoons over a girl's uniform and reveals her actual gender, he promptly freaks.
Also it's implied that before all these happened, Erika also had the same unsettling experience and stayed home with a fever like Tsubomi.
Black Butler: While undercover in a circus, Ciel shares a tent with a skinny teen that he calls "Freckles". Turns out that he is really a girl named Doll. She offers to show him her privates so he can be sure.
Played for Laughs with Karara's debut in the Keroro Gunsou anime: Tamama spends the entire episode flitting between jealousy at the thought of being replaced as the platoon's cute tadpole and being charmed by the new 'recruit's' Hero Worship of him. Then, when Karara heads home, she promises to become a good future bride for him...
In Adolescence of Utena, the Revolutionary Girl Utena movie, Utena is so bifauxnen that one of the main characters (Saionji) thinks she's a guy until halfway into a duel when he manages to cut her shirt open. While surprised, it's only evident in his choice of words, his face and voice remain as level as ever (for him) and he continues to attack her.
In Otomen, when he was a little boy, Kasuga developed a crush on his sweet, gentle cousin. Flash-forward ten years, and imagine his shock when he learned that his cousin grew up to be a tall, handsome guy.
In Karakuridouji Ultimo, Service, who up till then was the source of much Viewer Gender Confusion, got his shirt blown off during a fight in Chapter 23, revealing... a flat chest. We next see Yamato's face with an expression of pure shock. The fandom was mind-blowned too.
In episode 6 of Kampfer, Natsuru inadvertently does this to Mikoto when his identity is compromised. Apparently, his clothes only change during transformations if he/she is wearing the Seitetsu Academy uniform.
Iono the Fanatics: Well, Dropped a Bridget on Her really. However, inverted. Iono not only isn't uncomfortable with Tomo Senoo when she finds out the cute girl she was crushing on is a he, she's actually impressed.
Iono: Who would have thought even a dedicated skirt chaser like me could have been fooled.
Ice Revolution is one long series of dropped Bridgets after martial artist and extreme Tomboy (so extreme her hairdresser likens her to a fellow Transsexual) Masaki decides to take up the very girly sport of figure skating, culminating in her dropping a Bridget on an entire ice arena when she appears on the ice at her first public performance wearing a skating dress. Everyone at the rink had just assumed she was a boy up until that point.
Poor Masamunya has one dropped by the title character of Nyanpire seconds after developing a crush on him.
PG version in Cardcaptor Sakura. When Sakura, Kero and Tomoyo have to catch a Clow Card that has taken residence in a painting, they meet with a kid named Yuuki whose Disappeared Dad is the artist who painted it. At the end of the episode Yuuki's Nice Hat falls off and reveals very long Rapunzel Hair, thus showing the trio (and us) that Yuuki is a tomboyish girl.
Much to the shock of the heroes of Samurai Champloo, this is not the case with the tourist they meet in one episode. Granted he IS surprised to find out the kabuki actor he had a crush on is a man, but it's a pleasant surprise.
Author Mineyo Maya of Patalliro! Fans are shocked to find out that the shounen-ai author is a happily married man with three kids.
Inverted in Mayo Chiki!. The butler for a local rich girl, Konoe Subaru, is actually a girl. She was allowed to be a butler, which is a men's only profession, on the condition that she can hide her gender from the students at school. Her cover is nearly blown when Ordinary High School Student Jiro accidentally finds it out. But luckily for her, he agrees to keep it a secret (largely due to blackmail from said local rich girl, who also promises to help cure his gynophobia, or fear of women, as he suffers from nosebleeds anytime a woman touches him).
Jun Watarase of Happiness!, who dresses like a girl, looks like a girl, speaks like a girl and even has a crush on the main hero is actually a gay, androgynous boy which is revealed pretty soon. His motive for behaving like that is "because the female school uniform suits him better and does make him popular among male students." In the sequel for the game, Happiness! Re:Lucks a route of sorts was added for Jun, making him a valid target to pursue.
In an OVA, Jun temporarily does become a "full-fledged" girl
The backstory of Prism has Megu spending a romantic day with a boy back in grade school... only to discover on her first day of high school that Hikaru is actually a girl.
Code Geass: In the Turn 9.34 picture drama C.C., Kallen, and Lelouch dress up as belly dancers to sneak into the Chinese Federation. C.C. and Kallen introduce Lelouch as their "beautiful older sister" and the men ogle him. Of course, Lelouch has a masculine voice, so when he speaks, they realize that he's a guy.
However, this is unsettling to us... but the person they're there to assassinate is fine with Lelouch being a boy. As long as it's pretty...
In Moyashimon, a certain cute goth-loli attired "girl" is not all she seems. Oikawa goes on a rampage when this is revealed to her after she witnessed a kiss. It appears that Yuuki not only cross-dressinges but has a thing for his best friend.
A variation appears in Kuroneko Guardian. An actor is assigned a bodyguard who he believes is a boy until he walks in on her topless (when she was taking a shower).
Hanaukyō Maid Tai: Taro's maids (except the one who convinced him to dress up like a maid) got really shocked.
The protagonist of Sazanami Cherry gets one of these from their own sister. Their sister is considerably older than them and they didn't know she was transsexual.
Comics — Books
Even DC Comics' woman-lovin', homicidal, Anti-HeroBadassLobo has had this happen to him. In "Lobo's Big Babe Special", he is hired as a bodyguard for an intergalactic beauty pageant. But each of the ladies in the pageant has one nasty surprise or another (even the ones he knew!) and were subsequently eliminated. Each of them, that is, except the extremely busty T.V., the one Lobo has been drooling over the entire time. Once T.V. was crowned the winner, the horny Main Man made his move, despite her subtle hints that it wasn't a good idea. Finally, T.V. tells him to "put your hand here." I think Lobo and everyone reading now knows what the name "T.V." stands for...
Used, of course, in Liberty Meadows. Dean goes to a bar and sees someone who, from behind, appears to be a lovely long-haired lady. He proceeds to crudely offer to play some "tonsil hockey" with her before discovering that "she" is in fact a long-haired man.
Dean: Damn hippies...
In Camelot 3000, Tom Prentice awakens memories of Camelot in Sir Tristan's reincarnation, who happens to be a gorgeous young woman. Tom's instant crush on the reborn Tristan plays out this trope. Ultimately it proves hopeless, as Tristan refuses to accept life as a hetero female, eventually entering a lesbian relationship with Isolde's reincarnation.
In Promethea, this happens to Dennis Drucker, who finds out that his goddess lover (one incarnation of the eponymous Promethea) is actually comic book artist William Woolcott. This ends about as humorously as most Real Life examples of this trope.
Between X-Men characters Scott, Jean and Warren in Marvel 1602. Jean is a Bifauxnen who has been disguised as "John Grey" as part of her education, and when Warren shows up, he starts hitting on her. Scott confronts him angrily, revealing the secret that Warren must have obviously glimpsed... only for Warren to reveal he had no idea "John" was a woman.
Grant Morrison's Zenith had the title character propositioned by Metamaid, an attractive pre-op transsexual superheroine. After Zenith finds out, he passes the buck to the naive young superhero TNT Tom by suggesting that he and Metamaid might like to get acquainted. At least it apparently ends happily for both parties.
Zenith: TNT Tom left with a smile on his face, mind...
A slightly different version used in the sequel to A Very Potter Musical: the gay Dumbledore falls for the rather mannish Professor Umbridge (who, incidentally, is played by a man), and is shocked and horrified when he discovers that she doesn't have a penis.
In the Spider-Man fanfic "Blessing In Disguise," Harry discovers that Peter Parker has turned into a girl when he startles her and she falls out of the shower in the locker room on top of him.
In the Puella Magi Madoka Magica fancomic Thanks Kyubey, a emotionfied Kyubey is turned into a human. Mami and Sayaka hoped Kyubey would be a hot male. They are not amused when Kyubey turns into a Moe girl.
A literal unsettling gender, as opposed to sex, reveal in Hivefled; one of the many sources of Gamzee's current trauma is that his bloodlink's offhanded comments about Gamzee being feminine got him seriously thinking about his gender identity for the first time in his life and realising that he actually is genderqueer, though he doesn't currently know there's a word for it.
Films — Animation
Francis the ladybug in A Bug's Life has to constantly reveal his true sex. And given he's voiced by Denis Leary, he does it in the most caustic way possible.
In Ace Ventura: Pet Detective, Ace Ventura figures out that detective Lois Einhorn is actually Ax Crazy former professional football player Ray Finkle and is responsible for the kidnapping of the Miami Dolphins's mascot Snowflake and quarterback Dan Marino. He then remembers that Lois had tried to make out with him earlier. He gets Squicked. Badly. Later, when Ace Ventura exposes her former identity to the rest of the police force, all the twenty-odd policemen present, Dan Marino and the dolphin also get Squicked. Apparently she got around... (and as a shout out to make it funnier, the song playing in both sequences is Boy George's "The Crying Game")
Roger Podacter also found out, presumably during an intimate encounter with Einhorn, and as Ace declares during the reveal, that's why he wound up dead; "He found Captain Winkie!"
The Associate: A gender-swapped version of this trope occurs when Camille Scott, a business associate of main character Laurel Ayres (a black woman), goes public with a story about being pregnant with the child of Ayres' business partner, Robert Cutty (an elderly white man) after Cutty refuses to sleep with her when they meet privately one evening. At the climax of the movie, Cutty reveals that "he" actually is a well-disguised Ayres.
In Without A Clue, Reginald Kincaid (playing Sherlock Holmes) is quite attracted to a woman impersonating Lesley Giles. The real Lesley Giles , who has been abducted, is a man who habitually dresses as a woman. After Giles is rescued, "Holmes" and Watson manage to palm Giles off to Lestrade, claiming (truthfully) that Giles "appears on the stage in Paris", in an act called "Les Femmes Faux".
In Trainspotting, Francis Begbie picks up a woman in a club. Outside, in the car, he's making out with her, then goes to rub her down there, and finds she has a woodie...
Played for laughs briefly in Blades of Glory. When several people are interviewed to see how they feel about the male/male pair skating of Chaz and Jimmy, one guy comments in surprise "Wait, the blond chick's a dude?"
Tanya's silhouette reveal as (possibly?) a joke in The Naked Gun 33 1/3. The DVD commentary revealed it was a stand-by and they were going to use a hairy butt instead. Luckily, the cable TV airing show this variant, while movie channel keep the silhouette intact.
Played straight in the Japanese rock 'n' roll zombie epic Wild Zero, when the male lead finds out that the girl he's been chasing all movie is actually a guy in drag... then wondrously averted when the god of rock and roll himself tells the guy not to be such a wuss, as love knows no gender. One of the best film lines ever:
Guitar Wolf: ACE! Love has no borders, nationalities, or genders! DO IT!!!
As you can guess by its title, Victor/Victoria provides a few perfect examples of the reverse of this. The one that stands out most is when Victoria, dressed as Victor, pulls Norma into a bedroom and acts as if she wants to have sex with her. Norma later bursts out of the room and proceeds to yell angrily at her ex(?)-boyfriend (who is now dating Victoria) that Victor is a woman.
Is the plot of a Mexican comedy Los Dos Rivales.
At the end of Tomboy. Laure is forced to don a dress and her mother makes her apologize to the boy she fought earlier. She also goes to visit her girlfriend, thus making the reveal to her too.
In Rat Race, Owen drives a bus full of I Love Lucy fans dressed in Lucy costumes. One of them asks for a pit stop as the bus' bathroom door was broken.
Owen: So? You ain't got nothin' these other Lucys haven't seen before! Lucy: [in a deep voice] Not necessarily.
In Good Luck Chuck, Chuck discovers that one of the many women he's been sleeping with to help them find their true loves was formerly his classmate - and a man.
There is a pornographic story that was written in first person, in which the narrator makes love to a man. In the last sentence of the story, it is revealed that the narrator is also male, which is a revelation to the reader.
Done with a twist in the Darkover novel Hawkmistress: The main character is a young woman disguised as a young man, and is traveling with a group of mercenaries. The leader of the group starts hitting on her. She figures he's seen through her disguise; turns out he's gay.
At the end of the third Sir Apropos Of Nothing novel, Tong Lashing, the revelation that evil crime syndicate leader (and Apropos' brief lover) Verah Wang Ho is a man leads to his (anti)Heroic BSOD which ends with the Hiroshima-like destruction of the city they're all in.
In the Neil Gainan short story "Changes", all possible reactions to this are explored as a drug allows quick, easy sex-changes in a few hours. The few people in story who can always tell someone's birth gender, well, the one shown is the subject of severe violence when she denies entrance to certain clubs (this was her job).
A variation of this happens to Ivan Vorpatril in Lois McMaster Bujold's A Civil Campaign when he, realizing how slim pickings were for long-term female companionship, decides to intercept his old (and older) lover Lady Donna Vorryuter on her way back from Beta Colony (something related to an inheritance dispute surrounding her brother the late Count Vorryuter) and perhaps renew matters with said divorcee. Now who is that fellow with the black beard accompanying the Vorryuter Armsmen and why do his eyes look so familiar?
In the novel Trainspotting, it happens to Renton, not Begbie. Furthermore, he doesn't panic, but admits to always being curious about what it would be like to sleep with a man. Taking advantage of the opportunity, he ends up getting to third base; however, his friends then walk in on him, scaring Renton off any same-sex encounters until he finds himself in London without a place to spend the night.
In Moon Over Soho Ash Thames (one of the river spirits from the Upper Thames river) picks up a girl in a bar, when he gets her into bed he discovers she is a very convincing crossdresser. It turns out not to bother him, because in his own words...
"We were having so much fun I thought, 'why stop?'"
In Let The Right One In, Oskar finds out that Eli is actually a castrated boy. He doesn't mind, though. The Swedish film includes this plot point but is a bit more ambiguous about it, while the American remake mostly removes it, and a deleted scene suggests that Abby is probably is an actual girl.
In Ringu, Sadako appears to be a supernaturally beautiful woman but is a hermaphrodite with fully formed testicles. When the last carrier of smallpox tries to rape her he discovers this, freaks out, kills her, and throws her down a well.
In Getting Personal, three friends place personal ads for each other. They don't manage to find the person one of the trio met and was attracted to, which is revealed to be because she was a woman (although whether this is just a reveal to the audience/her friends, or whether she didn't realise either, is left unclear).
Song at Dawn It happened to Estela and Dragonetz individually concerning the same person: Sanchez, one of Alienor's Ladies in Waiting.
Dragonetz was crusading and saw some thugs about to rape a woman after killing her husband. They ripped open her dress and the surprise they found was great enough for Dragonetz to kill them with ease.
Discovering the same thing was part of Estela's 'initation', so to speak, into Dragonetz' inner circle.
Korean drama Coffee Prince is actually an odd example. The manager initially thought he was in a gay relationship, and was hesitant for this reason. But since he was trying to avoid arranged marriages and was so shocked to suddenly find this out, even though it was a workable relationship.
In Kamen Rider Double, the heroes use Wakana as bait to attract the Liar Dopant. Of course they couldn't really put Wakana in the line of fire. It's Philip in a dress and wig.
In the episode of Quantum LeapWhat Price Gloria, Sam uses this trope to enact revenge on his (female) host's boss for his treatment of her best friend. Sam convinces him that his host, the woman he'd been lusting after all episode, is secretly a man, playing with this trope even though the host has always been a woman.
Another sexuality-inverted instance occurs in an episode of 3rd Rock from the Sun, in which a Guy Of The Week dumps Sally when he finds out, to his dismay, that she isn't a guy in drag.
NCIS has a first-season episode "Dead Man Talking". While investigating a missing embezzler, Tony ends up on a date with a woman connected to the missing man. Then learns that she is actually the missing embezzler. Afterward, Kate rarely missed an opportunity to remind Tony of the incident.
Happened once to Sanchez from The Closer. He made the mistake of hitting on (and kissing) a pretty female witness...who turned out to be the perp in drag. In a somewhat darkly humorous twist, this was the incident that convinced him to start actually going to the mandatory therapy sessions with the department shrink. (Mandatory due to the fact that he was still suffering from PTSD after taking the bullet in the previous season finale; up until this incident, he'd been in denial about it.) Poor, poor Sanchez.
Farscape episode "The Flax", D'Argo discovers that the scavenger Staanz, who appears to be a rather ugly male, turns out to be, in fact, a female of her species, and is "considered quite the looker". This becomes Squick material for D'Argo when Staanz announces her attraction to him.
Briefly lampshaded at the end when a shaken Crichton asks Aeryn if she's actually a woman (which she is).
Inverted in an episode of The Drew Carey Show where Mr. Wick is challenged to find a crossdresser on the floor, after looking for a while Dionne Warwick walks in and Wick declares her a drag queen and grabs the music legend in her crotch. It turns out that it was the real Dionne Warwick much to Wick's embarrassment but she seemed to like being groped by him and remarked about how friendly the stores staff was.
Doctor Who: The Doctor actually manages to do this to himself after his regeneration into Matt Smith.
In the "Who Can Bone More Women?" Contest on Kenny vs. Spenny, Kenny hires a pre-op transsexual to get all buddy-buddy with Spenny. Spenny racks up points like crazy until The Big Reveal at the end. He is not happy.
One episode of 1000 Ways to Die featured a rapist targeting a lady as she left a gym. As it so happens, the "lady" was a cross-dressing semi-pro boxer, who killed the rapist with one punch.
Inverted on Reno 911!: Dangle once had sex with a woman he mistook for a man in drag.
Chicago Hope did it in the middle of its run when one of the doctors, a very manly hockey player, starts dating Mia Sara. When she informs that she has something to tell him, he says that he already knows... that she has fake boobs and he's fine with it, she informs him that she actually used to be his best friend and hockey teammate in high school.
There's Something About Miriam features a sexy lady called Miriam and a group of stud males trying to woo her attention. Except that Miriam is actually a pre-op transsexual - something the participants had no idea of but which the audience knew right from the start of episode one. The whole thing led to some of the competing men suing the TV network. And as one can imagine, transgender advocates were not thrilled at the show setting the movement back to the stone age.
Similarly(ish): post-op Transsexual Nadia Almeida, who won the fifth series of Big Brother UK didn't tell her housemates of her... "situation". Said Bridget was Dropped upon evicted housemates in her post-eviction interview, until LGBT right campaigners complained about five weeks into the game.
Barry Zuckerkorn apparently seeks out this trope, exclusively:
Barry: Hey, you’re not one of those silly men that’s dressed like a woman, are you?
Prostitute: No, baby, I’m the real thing. (Barry floors it and drives away.)
One episode of Law & Order: SVU involves a pre-op transsexual who appears female in every conceivable way except actual plumbing, who apparently killed a friend of her boyfriend's to prevent a public revelation. When the SVU team confront the boyfriend (ignorant of the fact that the boyfriend had no idea his girlfriend was biologically male), he runs in, grabs her by the groin to determine sex, and then runs out to commit suicide with an overdose of heart condition pills.
A judge then decides to send the extremely convincing transsexual to a men's prison because of her plumbing. She is promptly gang-raped and beaten. We are shown the aftermath, with her headed to a hospital, strapped to a gurney, basically a solid swollen bruise.
In an episode of Dark Angel, politically and socially conservative Normal discovers that his love interest is a trans woman. Unusually, he remains interested, but is dumped after she realizes she's a lesbian.
Bones: The subplot of an episode revolved around the team trying to figure out whether a Japanese assistant is a man or a woman. It is debated at some length before Angela figures it out in her own way. The character is a man...the actress is a woman.
Another episode has the team realize that the victim was a post-op male-to-female transsexual. This had absolutely nothing to do with the murder.
An episode of Diagnosis: Murder plays this straight (as it were). The victim was an MTF post-op TS, and Steve had been flirting with her before she was killed. To the show's credit, the victim was portrayed as a sympathetic character and none of the main characters freaked out about it. In fact, she was killed by her former military buddy because he was squicked, and the murderer is portrayed as a Jerk Ass.
Will and Grace: Jack freaks out when he gets turned on by the stripper at Leo's bachelor party, until he finds out the stripper is a pre-op who dances to raise money for her operation.
In Two and a Half Men, Charlie Sheen meets an old flame who has had a sex change and become Chris O'Donnell. He is freaked out by it but eventually comes to terms with the idea until his mother starts dating his ex.
Charlie:... and this will be the name of my biography Me and my mom had sex with the same man.
Also a Running Gag is a certain Noodle Incident where he hit on a woman who later turned out to be a man. And from such statements it was pretty obvious but Charlie was too drunk to notice at the time.
Charlie: How was I supposed to know?"
Alan: She had an Adam's apple the size of my fist and could palm a basketball.
A one-episode B-plot in Century City followed a lawsuit a man filed against a female-looking Hermaphrodite for causing him to question his sexuality. The case was dropped when he turned out to be a transsexual too, but an in-universe ad for penis attachment surgery led to the observation that "someone should sue somebody for something."
Nip/Tuck: In an early season, Matt starts a relationship with an older woman named Ava, much to the displeasure of his three parents. (Sidenote: It's f* ck'n' Famke Janssen! WHO WOULDN'T!?) Christian seduces her in an effort to get her to stay away from Matt and immediately deduces she used to be a man (and later describes her as "the goddamned Hope Diamond of transsexuals").
After Matt finds out about Ava and she has disappeared, he trolls bars until he finds an obvious transsexual, but as they start making out, Matt discovers she is pre-op and beats her violently.
In one episode, Herb starts flirting with a woman who claims she knew him in high school. While making out with her, he learns he did know her in high school... before she had the operation. She was a teammate of his on the high school football team, in fact the center to Herb's quarterback. To say Herb had a case of the Squick is putting it midly.
In an earlier episode, the trope is invoked and subverted by Johnny. To get Herb to stop hitting on Jennifer, he tells Herb "Our receptionist, the beautiful Jennifer Marlowe, is a result of the most cunningly successful sex change operation in the United States!" The ploy works... sort of.
Double Subverted in The IT Crowd when, in a B-plot, Douglas embarks on a successful relationship with a post-op transsexual woman — but it comes crashing down when he realises that she was saying "I used to be a man," not "I'm from Iran."
Community: Pierce has to be corrected as to the gender of the singer that made Hawthorne Wipes a gay icon. The same singer is seen later on, arm in arm with Chang, leading to this beautifully ironic line:
In one episode of House, a beautiful teenage model appears to be female, but turns out to have Complete Androgen Insensitivity, with her symptoms being caused by a tumor on one of her undeveloped testicles. She is horrified to discover this, as is her manager/father, with whom she had been having sex. House's response to the manager's horror is priceless:
House: Oh, sure. Now it's creepy.
The music video for the song "Smack My Bitch Up" by The Prodigy does this to the viewer. It's a first person-camera accounting of a night of drunken carousing, drug use, and barhopping in which the protagonist gets into at least one fight with some guy, and molests a girl in a club, ultimately ending the night with a hooker. It's then revealed by a look in the mirror that the protagonist is actually a hot chick herself.
"Well I'm not the world's most masculine man / But I know what I am / And I'm glad I'm a man / And so is Lola"
The second version of "Uneasy Rider", when the singer and his friend go into a gay bar and the friend goes off dancing with a lovely lady.
I grabbed her hair Came off in my hand And that beautiful girl Was just a beautiful man.
a portmanteu of CHIcK (in the girl sense), SInangag (Fried rice) and ItLOG (egg, specifically a sunny sideup); [Viand Name]silog is a popular meal in the country. Culturally translated, it effectively means "A Chick with eggs".
The Doug Anthony All Stars song Sailor's Arms also has this theme.
Pet Shop Boys' "One thing leads to another". The protagonist gets drunk, picks up a woman in a bar, attempts to make love to her, and discovers she's has a penis. He drives off, confused, and crashes his car and dies.
The lead singer/guitarist of The Silversun Pickups has a very high register, causing a mild version of this for someone who hasn't seen them perform before.
One of Aerosmith's '80s comeback singles was "Dude Looks Like A Lady," with a line that goes, "Love put me wise/To her love in disguise/She had the body of a Venus/Lord, imagine my surprise!"
Biz Markie's "A Thing Named Kim": "She didn't look none like she looked across the room/She had big broad shoulders and her titties was big/They were filled with silicone, and her hair was a wig... So I hurried out and left, she said, "Please stay"/I said, "Sorry money grip, I don't go that way"/So I stepped out in a hurry, to gather my wits/And thought that's a damn shame, he had nice tits/And that's the last I ever saw of Kim/You wanna know why? Cause she's a he and her's a him." Needless to say, Markie didn't win many GLAAD awards for that one.
In a rare example that has nothing to do with appearance, most people are surprised to learn that Angela Gossow, the vocalist of Swedish band Arch Enemy, is a woman. Why? Well... just listen.
Most J-Pop stars utilize this trope as a way to gain fans. Notable examples include Miyavi and Gackt (though Gackt is quite competent at expressing his masculinity when need be). The latter was also a major inspiration for many of Tetsuya Nomura's character designs. The Crisis Core character, Genesis Rhapsodos was directly modeled after him.
It's also getting harder and harder by the month to tell what gender Miyavi really is (male).
"Luisa" by the Peruvian band Chabelos. It's about a guy who falls in love with a hooker called Luisa, and then discovers that "Luisa" is a transvestite, and he thinks that's hot.
In Wilfrido Vargas's "Macho Man", a guy falls for a pretty girl that he later finds out, while they are almost intimate, is a pretty boy; he freaks out and runs away, losing his shoes in the process.
In Rodney Carrington's appropriately named "I Think I'm Dancing with a Man" the singer begins to get suspicious of the woman he's been dancing with because of many masculine traits. His friend then takes "her" for a dance and "her" skirt falls off confirming it.
Tone Loc's "Funky Cold Medina": "But when she got undressed it was a big ol' mess... Sheena was a MAN!"
EPMD's "Jane 3" off of Business As Usual: It all starts when Erick & Parrish befriend a hard gangsta named Jay... but when they visit "his" pad, the decor (and bathroom contents) don't seem right...
Schoolly D's "Saturday Night": "What I thought was a girl was nothin' but a fag" (Needless to say he's not gonna win any GLAAD awards either)
A common prank that people pull on the internet is to post a picture of a hot girl for everyone to oggle, only to reveal that the hot girl is really a very feminine man.
Some goons at Something Awful did this by making a female Myspace profile with the lone picture of some cleavage, later revealed to be a guy pressing his manboobs together.
Occured on a huge scale in an issue of Maximum PC with an advertisement. Sufficient numbers of people were surprised that the actor was male, that it was mentioned in the letter from the editor in the next issue. The ad in question featured Toplessness From The Back, but a very effeminate male.
WWE wrestler Mark Henry ran into this trope years ago when he found out that a lady named Sammy which he fancied really had a dick.
"Oh sweet Jesus she has a penis!"
The Eberron setting of Dungeons & Dragons actually notes that this possibility of this occuring is one of the main reasons for the Fantastic Racism leveled against the shapeshifting Changeling race, whose members are fully capable of changing not just appearance but gender at will, regardless of the gender of their actual native form. It's a well known joke in Eberron fan circles to point to any depiction of an attractive male or female character and declare that it's really a changeling of the opposite gender.
Nevermind that picture from the Sharn sourcebook that showed a couple of the working girls in the red-light district. The jokes that picture alone spawned...
While technically androgynous in the new fluff, Daemonettes from Warhammer 40000 will play this trope on one of their victims just to watch them squirm. Because, you know, that's what they do. (And then they gut their victims like pigs with their claws, which can go through Power Armor like a knife through butter.)
In A Very Potter Musical, Dumbledore was dating Umbridge for a bit when he thought she was a man in drag. He was disappointed to discover the truth.
Bridget, the Wholesome Crossdresser teenage boy in a nun habit from the Guilty Gear series, and former Trope Namer. In Bridget's birth town there was a superstition that if twins of the same gender are born, disaster will come. Rather than let the town sentence him to death, baby Bridget's parents put him into the custody of the local convent's nun who raised him as a girl. Bridget's gender is never a secret in the game, at least not to the audience, and is spelled out right at the beginning of his storyline. He also never intentionally hides that fact (anymore; it's a long story), thus only a few characters actually get the unsettling reveal. The problem is that most other characters simply assume he's a girl, either because he's lived most of his childhood as one or because of his Moe Moe nun outfit.
Even Zappa from Guilty Gear XX has a Bridget dropped on him in Story Mode. As written in a letter to his mom (which he writes during his brief periods of lucidity), he says he found an injured young girl by the side of the road who he wished to make his wife. (He is unaware that he is the one who pounded her into the pavement). But when he attempted to pick her up and carry her, he finds...
At least he isn't in Johnny's shoes. That poor goon has a story mode ending about finding out too late that Bridget is a guy. ("I can't believe I hit on another man!")
Not to mention a little Yon Koma about Axl trying to hit on Bridget. Bridget gets fed up, grabs his arm and pulls it below the panel, with the word "TOUCH♡". The final panel has Axl gripping said hand with a horrified expression, going "What the hell did I just touch?". And "DESTROYED" in large letters above him, referencing the One-Hit Kill attacks from the games.
Over here in Real Life, people have found it quite amusing to show Bridget to those who aren't familiar with the Guilty Gear series, and get their reactions when they drop the bombshell, as it were (she and other characters of this trope are called "traps" for this reason). As the meme says, "Everyone is gay for Bridget".
Leisure Suit Larry has this happen in both the sixth game ("Shape Up or Slip Out!") and the eigth game ("Magna Cum Laude").
And for the most famous female example, you have Sheik of The Legend of Zelda: Ocarina of Time. Earlier in the game, Ruto called "him" a man. She was wrong. You know that you have an epic gender reveal when the fandom spends ten years starting Flame Wars over it.
The Alraune trap is brought back again in Disgaea 4 when the Cute Monster Girl in question is revealed as a guy in front of "her" adoring fans. Said fans decide that they "don't mind a little trap action."
In Dragon Age: Origins, it turns out that Shale was actually once a female dwarf. Thanks to The Fog of Ages, even the character in question is stunned by this, making it a rare case of the character in question experiencing the unsettling reveal.
In Metal Gear Solid 2, Raiden, a shameless Bishōnen, is revealed to the President of the United States. The president literally grabs Raiden's package to check his sex, reacting in suppressed shock when he learns the terrible truth — the script says he'd misidentified him as the similar-looking female terrorist leader, Olga Gurlukovich, but Raiden's decidedly male voice and obvious bulge should have put that suspicion out the window. Besides, why didn't he just ask Raiden?... What was he planning to do to Olga?! Who voted for that?!
Averted with Libra. He mentions after being called a sister by Chrom that he's actually a priest. When he apologizes, he mentions that it could have been awkward. Very awkward. Very Very awkward. Unsurprisingly, Chrom tells him to stop.
Things indeed become awkward in Libra's supports with Virion, who continues to flatter his beauty even after finding out he's a man.
It might be a trap for players to trap players who are expecting a Trap, but there is a masked young man who claims to be Marth, and backs it up by wielding Marth's legendary sword, the Falchion. People are already very aware of Marth's gender at this point, right...? Turns out, this "Marth" is an imposter... and a girl. Yeah. Marth is A Girl, and a very beautiful one too.) (You may now squee).
Flea from Chrono Trigger has confused generations of gamers with his/her claim that he/she is actually a guy, despite having obvious cleavage in the artwork. Not to mention the actual heroes, of course. Luckily Flea plays no role whatsoever in the story other than to be a Mini-Boss.
Final Fantasy V. The leader of a band of pirates called Faris is assumed to be a male due to occupation, but once the party gets halfway through the second dungeon it turns out he is a she. To quote a boss later on in the game, And now we shall fight like men. And women. And women who dress like men. She even occasionally mistaken refers to herself as male. It's clearer in the original Japanese, where gender is reinforced by speech much more than in English. (For example, Japanese has gender-specific first-person pronouns, not that this stops some people.)
Final Fantasy VII: It's possible to get the Don to choose Cloud, in which case he reveals that he was in drag. While the idea of the Don picking Cloud over Tifa and Aerith may seem silly and unlikely based on the graphics in the original game (and their low polygon count), the Don's decision becomes much more understandable if one looks at Cloud's character design in Advent Children, especially if Cloud-in-drag appeared anything like THIS◊. Stupid Sexy Cloud.
In Fate/stay night, there's a reason why Guinevere had that affair with Lancelot, since her husband, King Arthur, aka Saber, turns out to be a woman (and stopped aging at the age of 15), but Guinevere agreed to the marriage as political fiction only, and due to that reason Arthuria never blamed Guinevere nor Lancelot for their romance and was forced to take action against it by her enemies.
This also occurs in the prequel series Fate Zero, where Kiritsugu is quite shocked when he summons King Arthur and finds himself face to face with a young woman. While Saber initially thinks that it's because he's displeased by her sex, Kiritsugu's wife Irisviel explains to her that it's more than he's saddened because he realizes what Saber was forced to go through, including hiding her identity.
The Digimon series has played with Renamon's gender (or lack thereof) for some time, but Digimon World Data Squad amped it up by giving us a male Renamon with a painfully obvious female voice (in fact, it was the same voice actress who played Renamon in Tamers). Let's ignore the Unfortunate Implications of a male Sakuyamon.
Shika in Kira Kira, when a guy fell in love with him when he was forced to cross dress. Two years later, he was shocked to realize that Shika was in fact male, but quickly got over it even offering to be his wife since the idea seemed to make him uncomfortable.
Iita in Blaze Union. Oh, ye gods, Iita. She's a perfectly adorable little Fille Fatale, cute and squeaky and very girly. Then night falls, and the other half of her Split Personality takes over — the side that is male, brash, Hot Blooded, and downright thuggish. Her male half cheerfully announces to the stunned women of the game's cast that "oh right, sorry, I forgot to say: I'm a man at night". Equally shocking to people who first see Male!Iita and then realize that what they thought was a boy dressed in girl's clothes is actually still physically female.
Sting is all too happy to play with the latter situation, by the way; as is the norm, a number of Fanservice-y phone cards are being produced. One features Male!Iita smirking and slowly peeling the clothes off of his very female body.
While the title heroine of Atelier Annie has her moments due to her (unfortunate) Bifauxnen status, the game also gives a somewhat bizarre example when some men tried to hit on, of all people, Hans. The bizarre part is that they genuinely mistook him as a girl, while his co-workers in the Committee see him as a guy just fine.
Unsurprisingly, the Camwhore class in Forum Warz has this as a standard attack, if one not often seen. (It's down the line of a skill chain which many players respec out of before obtaining it.) Note that the gender, age and race of every player character is defined as "whatever happens to be squickiest at this instant". The same applies to any NPCs who use multiple or artificial personas, eliminating any potential shock value out of gender. (Especially as very few players would be attracted to most of the NPCs.)
Erica from Catherine is actually a post op transsexual. However, Vincent, Orlando and Jonny are aware of it, and there are several hints dropped over the course of the game before the actual reveal. It's only this trope to Toby, who lost his virginity to her.
Dark Souls has the Dark Sun Gwyndolin, the last born son of the Lord of Sunlight, Gwyn. Because of his lunar magic and association with the moon, he was raised as a girl.
The Pokémon Kirlia, Gardevoir and Lopunny have extremely feminine appearances. And a fifty percent chance of being male. There's also Gothitelle and its evolutionary line, which have a slimmer-but-still-possible chance at twenty-five percent.
This joke was done as a gag during a scene where Hal is trying hit on women in episode 6 of Bowser's Kingdom.
Inverted in the "Blood Gulch Chronicles" seasons of Red vs. Blue with the character Tex, who is mistaken to be a guy, but is actually a woman to say the least. Played Straight with the character Donut, whose pink armor has gotten him mistaken for a girl, at least in the earlier episodes.
Amber from Khaos Komix thought Nay was a Boy when she first met her.
In El Goonish Shive, this happens quite a lot when someone's stepped out of their normal gender. Somewhat unusually, it often gets milked for some drama in the process.
Justin and Susan almost do something they'd regret later while both gender-bent for Grace's birthday party. Good thing they didn't, since Justin likes guys; things would have gotten awkward once Susan became a woman again.
The "Sister" arc was full of this. Minor characters were falling at Elliot's feet, and that's before Ellen took on a life of her own.
The Wotch manages to do this to both participants, here when Jason is transformed into Satyr Sonja he has random flirty outbursts he can't control. When he "puts the moves" on Robin they both freak out. Jason continues to flirt-and-freak throughout the arc. And one flirt-and-freak recipient winds up wanting to date "Sonja" later.
A rather ridiculous case when the two similar-looking characters in the rather ambiguous fighting game (within a webcomic) "Loli vs. Shota", both finally decide to actually check their genders... and are shocked to find out that they're both wrong on which one they thought they were. And yet even though we learn they're both wrong, the reader still is left in the dark about which character is which gender.
A Running Gag is that masculine characters tend to have sex with Freddy... who, despite having breasts, is male and revels in it. They tend to be very drunk at the time.
Averted very carefully by Vaarsuvius, an elf whose gender remains unspecified (and just to keep the readers guessing, the gender of V's lawfully wedded spouse is also unspecified and their kids are adopted.)
Invoked when Belkar hits on a magically gender-swapped Roy. Turns out, he knew it was Roy the whole time, and he was just doing it to squick him out.
Concession: Artie wakes up to discover he has engaged in inappropriate acts with hypersexual preteen Chelsie Warner while in a brain-tumour-induced — or, as it turned out, Joel-induced — trance, and confides in his boss:
Artie: But honestly, I'm not sure what disturbs me more... the fact that this happened, or the fact that Chelsie is actually a boy.
This almost happens during an occasion where Joel, Matt, and Aaron "Nicole" O'Connor meet with a crude ursine associate of Joel's who initially believes Nicole is a girl after Joel introduces them. Needless to say, said ursine friend is moving to kick Joel's ass when he finds out the truth of Nicole's gender.
Dan infiltrates Twink Territories dressed as a woman. Later on, Biggs finds out. Quoth Biggs: "I'd probably feel more awkward if this was the first time this had happened..."
In another story arc, the shapeshifting incubus Abel takes a job working at the Lost Lake Inn. Dan gripes that it'll be an unfortunate adventurer who comes into an inn hoping for the traditional greeting and service by a perky cute beer wench. Abel: "Oh, well if THAT's your only issue..." Dan * turns around to see Abel has put on a very convincing female form* "YIGG!" Page caption: "Don't worry, adventurers are used to dealing with traps."
Later on Dan meets Mink, who is androgynously pretty, flat-chested, and runs around in a skirt and no shirt. Dan outright asks Mink whether they are a boy or a girl, only to find that Mink has forgotten hirself (being another shapeshifting 'cubi). Mink is on the point of taking a peak down hir skirt to refresh hir memory when Dan decides that he doesn't really need to know that badly.
Venus Envy has this happen to Lisa when she assumes that Chris is a male-to-female transsexual only to discover that he's actually just a Wholesome Crossdresser. Chris gets experiences this trope when he first meets Lisa and Zoe, assumes they're crossdressing boys as well, and grabs Lisa's breast while telling her it "looks totally fake". They beat him up.
Material Girl, in which the character the title refers to isn't really a girl.
Used in MegaTokyo early on, when Piro is reading through a section of girl's manga in a shop in Japan. A Japanese schoolgirl seems to think that Piro is a girl and is "cute". Her friend informs her that Piro is, in fact, a guy.
A double inversion of this trope occurs in Teh Gladiators, first when the Murlocs that join the heroes turn out to actually be female, and then when one of them, Yolanda, develops a crush on Vallant rather than vice versa.
Averted by the Elle-Boys of J.E.T. T.E.E.N. Despite looking exactly like girls, they make no secret of the fact that they're actually boys. As a rule, they're also heterosexuals who exhibit many "traditionally masculine" traits.
In the story "South Pacific Powder-Puff Power!"note Jet Dream and her T-Girl Counterspies #3, there's a startling revelation about a longstanding character. The T-Girls learned that Ting, the Polynesian princess and only "female" member of the Thunderbirds, had actually always been a male. In Ting's matriarchal tribe, male royals are expected to live as women. When the rest of the team changed sex, so did Ting.
Reversed in Kevin & Kell. Rachel, upon first meeting Bruno, tries to romance him because she thought he was a sheep. To be more specific, not a male sheep. (Rachel's a rhino with bad eyesight, and had gone by the smell of the sheepskin Bruno was wearing, which was made from his girlfriend Corrie). The end result was Bruno added ram horns to the sheepskin so he's never mistaken for a girl again.
Inverted and double-teamed in Roomies with Corey and Dave(ina).
Sexy Losers loves playing with this trope. Most notable is one comic in which a man picks up a woman with short hair at a bar, only to take her home and discover she is a woman, but he's gay and he thought he was hitting on a man to begin with.
Would that be a booby trap?
Another Sexy Losers strip has one guy get a pregnancy scare from his girlfriend ("I'm not on the pill"), only for her to reveal she used to be a man.
Another has a man approach a suicidal woman whom he asks for a BJ before she jumps. After the act, he asks why she was going to jump. Turns out her parents disowned him for dressing up like a woman. So the guy jumps before the cross-dresser does.
One Manly Guys Doing Manly Things comic has Jared unsettled and warning Commander Badass that Poison was, in his words 'a dude'. Commander Badass then points out that it shouldn't matter what a person has in their pants unless you're planning to get into them. He's more surprised that Jared thought he had a chance to score with Poison, gender aside.
In the "Railway Children" arc of Skin Horse, Violet Bee tries to invoke this trope by revealing his gender to Tip. This plan falls flat because A) Tip was never particularly attracted to Violet and B) Tip is an Extreme Omnisexual.
Awkward 4 has a flashback sequence of a series of Alex's ill-fated blind dates, one of whom is a man who stammers "Alex" in shock and quickly checks to confirm that, yep, that's an adam's apple before running for dear life.
On the adoptable petsite Valenth, one of the NPCs is the person of intelligible gender of the week, Elliot Christoph. Considering many of the humanoid NPCs are like this, and all of them as such are men (plus the masculine name), many of the users expected Elliot to end up being male, referring to her as Sir Christoph and such. Elliot later is referred to as being female about twenty pages into the thread. The real kicker was the fact that she never bothered correcting them once. Lady looks like a dude indeed.
Desu Des Brigade: Professor Otaku admits in his Quick Hits review of Gravitation that he didn't realize Shuichi was male until he was halfway through an internet porn search of "her".
Prof. Otaku: Well... wow, she really likes it in the butt. Hmm... Why does she... Oh.
The Nostalgia Chick uses the Austin Powers "She's a man!" joke to express her doubts about Mel C being a real woman.
In the The Cinema Snob review of Sadomania, he repeatedly remarks how beautiful the female warden is and checks the back of the box to find out her name...and discovers she is played by "the stunning transsexual adult film star Ajita Wilson". Cue a horrified "Oh my God" followed by a Smash Cut of him sitting in the shower fully clothed calling Jillian on the phone claiming that they have to have sex "right NOW" since he's "so confused".
According to the video description, this was based on a friend of Brad's having had the same revelation.
In the Key of Awesome parody of Carly Rae Jepsen's "Call Me Maybe," Carly meets a cute guy at the club. The two of them get drunk, then go to her house and make out. The next morning, the guy wakes to find that Carly is actually a madman dressed as a young woman.
In the surprisingly serious short What's Opera, Doc?, Elmer Fudd finds out that the girl he fell for was Bugs Bunny in a dress — and actually kills Bugs with his magic helmet. Although it's unclear whether he does it because Bugs is male, or if it's because Bugs rejects him the moment the disguise is off! Or because, well, he's Bugs.
Bug: Well, what didja expect in an opera? A happy ending?
Pervert Glen Quagmire gets quite an unsettling revelation when he tells Peter and the gang that if he could have any woman in the world, he'd choose Taylor Hanson from the 1990s band Hanson.
Joe: Taylor Hanson's a guy. Quagmire: Oh! Oh! Y-you guys are yanking me. Hey, hey, let's put one over on old Quagmire. Peter: No, he's actually a guy, Quagmire. Quagmire: W-well, this is insane! That's impossible! Oh, my God. Oh, my God! Oh, my God, I can't... Oh, God! I-oh, I got all these magazines. Oh G-oh God! Oh, God!
Quagmire tends to get this trope fairly often. An episode where Brian is recruited by the force as a drug dog has Quagmire coming off a plane from Manila, where Brian comments:
Brian: And you had sex with two Filipino women. (sniffs again) And a man. Quagmire: You mean three Filipino women! Brian:(stares at him) Quagmire: ...Aaugh!
In a similar vein, Brian was the subject of a B-plot where he was completely frustrated over the family really not seeming to give any sort of care at all to him. Rather than coming home, he goes to a hotel bar, meets up with a woman, and they intellectually hit it off. After quite a few drinks he goes back to her room, and the next day is telling Stewie about his conquest... Only for Stewie to realize that the woman he was with had all the correct parts now, but just a couple days ago was Quagmire's father; the main plot of the episode was the man going through a sex change operation and how everyone around was dealing with it. When Brian found out, he had an impossibly long vomit session.
The Cleveland Show has a moment in the Thanksgiving special wherein Cleveland gets revenge on his wayward and emotionally abusive father by not telling him that the "woman" he's about to get in bed with is actually a man (and totally notTyler Perry / Madea). As it happens, the "woman" in question is actually Uncle Kevin, who disguised himself as a woman so Donna would have a positive female role model after her mother passed away. And then when Cleveland DOES tell him, it's not heard, but you see the two men gesturing... then the dad vomits for thirty seconds.
Futurama: There is the Valentine's Day episode in which Zapp Brannigan is on a blind date with a very burly man in drag, who leaves unexpectedly early...
Zapp Brannigan: Honey! Wait! You didn't show me your surprise!
Inverted in "War is the H-Word," when Zapp finds himself attracted to "Lee Lemon." He is quite relieved when he finds out it was Leela all along.
Zapp Brannigan: Leela! So it's you I've been attracted to! Oh, God, I've never been so happy to be beaten up by a woman.
Leela: Let's do it again sometime.
Also played with in Lrr (ruler of Omicron Persei 8)'s date with what he believes to be an Omicronian woman, who turns out to be a (human) cross-species dresser. He feels shocked and violated.
"I did not mean for you to find out this way. But I suppose what's done is done...DETECTIVE!"
And then later:
Terry: Lady, that is the sickest thing I’ve ever seen! You’re creeping me out!
Bruce: You?! She kissed me!
Note that this is Batman saying this, and considering his career, it should say a lot.
In a later episode of King of the Hill, Peggy befriends a drag queen, after discovering "she" has size 16 feet like her.
Done in a two part episode of South Park when Cartman, whose stuck in the future (long story, basically one of his usual schemes backfired), calls back to the past to reach Mr. Garrison whose recently had a sex change operation. Garrison is currently having sex with Richard Dawkins, Dawkins is the one to answer the phone and Cartman let's slip that Garrison is a post-Op. Needless to say Dawkins is repulsed. Not only that but by revealing this, it completely changes the future.