Due to the very nature of The Masquerade, one of the toughest things about it is finding other people who are also in on the Masquerade. This is justified since it wouldn't be very good form to go around asking everyone you meet if they know that there's a secret society of aliens or magical creatures living among normal people. If everyone does their job right, everyone in on the masquerade should appear like ordinary Muggles ... even to each other. This trope can lead to some really magnificent misunderstandings, especially in romance situations, and the most obvious sign is when you find yourself thinking "Now if they'd just been honest with each other, we could have avoided a lot of trouble here."
Of course, this type of situation could lead to many surprises. Suppose you're a mystical creature living in a world where mystical creatures are thought not to exist, and you must maintain the persona of being an ordinary person. You know that there are others like you that exist, but other than your close friends and family, you don't know who or where they are. You try your best to maintain your disguise, lying to all the muggles at school and at your job. But one of them is getting incredibly close to your secret. You've known this person for years and never thought him to be anything more than an ordinary muggle. But when he discovers your secret, it's actually okay, because he has the same secret himself!
In Fantasy Kitchen Sink situations (or crossover) they might have a completely different secret. If not a directly opposed faction, it's usually not a problem, as it is easy to agree to "not reveal your secret if you don't reveal mine."
Of course, it could work the other way around too. The trope is invoked whenever a character maintaining the masquerade discovers that another person, whom they've thought of for a while as an ordinary muggle, is revealed to them to also be a part of the Masquerade. Whether the second person has already known of the first person's involvement in the masquerade is irrelevant.
- Dokkoida?!: The series premise is a pair of superheroes fighting a group of supervillains on Earth as a test to see whose superhero suit is superior. Everyone, hero and villain alike, is given secret identities, with none knowing who any of the others are, and are under strict instruction to make sure their identities aren't discovered... then each and every one of them are placed in the same apartment complex due to budget issues.
- In Durarara!!, a great deal of the conflict in the latter bit of the series is the various factions of Ikebukuro butting heads (sometimes very very violently) and maintaining secrets from each other and the public. As such, many, many, many characters that interact with each other don't know that these people are actually part of the Dollars, or Saika's army, or Nebula, or the Yellow Scarves, or the yakuza, or...
- In My Monster Secret, Nagisa (alien) and Shiho (wolf-man) are neighbours and friends, but neither of them knows the other's real nature, despite Asahi and Youko knowing both of their secrets. They finally find out about each other in chapter 126.
- Both Minato Sahashi and his sister Yukari are Ashikabi in the Sekirei Plan. Since one of the major rules of the Sekirei Plan is "You do not talk about the Sekirei Plan", neither of them knows that the other is involved. It gets particularly frustrating because Yukari's Sekirei is an older brother to one of Minato's, and is devoted to finding her.
- When Minato and Musubi first move into Izumo Inn early in the series, Minato worries about having to keep the Sekirei Plan secret from their new housemates. It turned out that they're all Sekireis.
- Spy X Family:
- The premise of the story revolves around this. Loid is actually a spy (codenamed Twilight), and Yor is an assassin (nicknamed the Thorn Princess). Neither of them knows this about one another. Several others play out their own hidden agendas with all of them being equally unaware about anyone else. Anya, the Happily Adopted daughter of Loid and Yor in a false family, is the only exception to this because her Telepathy gives her complete knowledge of people's actual jobs and intents once she's near them or with someone else who knows. She naturally keeps this knowledge to herself for one obvious reason and also for her entertainment. However, there are some points in the story where the charade slips a bit.
- In Mission 12, Loid figures out that Yuri (Yor's brother) is a member of the Secret Police soon after meeting with him. In turn, Yuri is Right for the Wrong Reasons regarding his suspicions about Loid being a spy but understandably can't risk making a move at the time.
- Mission 16 has Anya in a precarious situation where somebody's in danger and she only knows because of her telepathy. She wants to tell Loid, but the fact she knows this despite not being anywhere near the scene makes her have an Imagine Spot about this scenario:
- There's a Golden Age DC Comics story about the first meeting between Clark Kent and Bruce Wayne - neither of whom have any idea the other one is also a superhero. (They find out before the end of the story when they both see the other changing into costume.)
- In Marvel Versus DC, Clark is working with the Planet's new photographer, Peter Parker, leading to a scene where they both try to make excuses to the other in order to change.
- Cassidy meeting another vampire in Preacher.
- The Disney Mouse and Duck Comics have some fun with this in their superhero stories, as the various heroes all know each other in their civilian identities but most secret identities are unknown,note leading to multiple shenanigans-especially because Paperinik (AKA Donald) is prone to wipe the knowledge of his identity from the memories of anyone who stumbles on it. Most notable (and funny) is when the authors remember that Daisy has one, as in those stories her and Donald hate but grudgingly respect each other's alter ego-and are also attracted to each other, much to their mutual horror (sometimes it's hinted that they've actually guessed each other's identity multiple times, only to forget through sheer denial).
- In Chronin, both Mirai and Gilbert are time travelers from the not too distant future (Mirai is from the 2040s, Gilbert the 2050s), who are stuck in 1860s Japan. For awhile they both keep up the pretense of being a normal person from that era as they travel together, with Mirai posing as a Rōnin, and Gilbert as an English businessman trading in Japan.
- The major point of the Battle Fantasia Project is that there was one called the Veil, which kept all the world's Magical Girls (and their respective antagonists) from being aware of each other's existence... then a Magical Girl named Akiko transforms on live tv before making an Attempted Suicide, is rescued by Fate Testarossa, and suddenly that masquerade is broken beyond repair. The result is magical girl forces from across the world joining forces and closing ranks to help protect each other better.
- Code: CONTROL: Much of the first chapter has the Lyoko Warriors and Ingrid, the new director of the Federal Bureau of Control, trying seperately to deal with XANA and an Altered World Event, respectively, with neither realizing the Supercomputer is responsible for both. The masquerade comes crashing down at the halfway point, after which both parties team up.
- Code Grid: Both the Lyoko Warriors and ENCOM make a point of keeping their respective virtual worlds a secret from others. The masquerade breaks when Keeva, Sam and Quora's daugther, is made the sixth member of the group, though she hasn't yet told the rest of ENCOM about this.
- Fate Azure Destiny: Ritsuka Fujimaru stumbles upon the secret war between Azur Lane and the Sirens. Just like the Mages Association have no idea about technologically advanced Shipgirls, Azur Lane and the Sirens have no idea about the Mages Association or that magic exists.
- FateBuild: The Mechanical Magus: In addition to the canon example of Shirou and Rin not knowing the other is a Magus, Rin was in the dark to the fact that Shirou is Kamen Rider Build. In fact, the magic side as a whole was blind to the existence of the Kamen Riders, who in turn didn't know that magic existed, until Shirou used Build to fight Lancer.
- Intercession: Sirius Black, escaped convict whom everyone knows is pursuing revenge on Harry, teams up with a mysterious witch commanding swarms of insects and seeking Harry for unstated purposes — each managing to convince the other of their own nefarious intentions because they think it's what the other one wants to hear. Fortunately, Peter Pettigrew is equally fooled by Taylor's persona, and throws himself on her mercy, believing her to be a fellow servant of Voldemort — and in the process, revealing Sirius' true nature, which soon gets things cleared up.
He exhaled, thankful he wouldn't need to muster up a convincing argument. They'd go after the rat. They'd get the rat. Then he would get rid of her, well before she would expect betrayal. She thought Harry was his prize, and that he needed her to get to him. Neither was true.
He could be as moderately pleasant as he wanted; he intended to hurt her son and belonged to a group who tortured and killed as standard operating procedure. She would feel no regret when it came time to betray him.
- In Not the intended use (Zantetsuken Reverse), three college roommates are a demon, demon summoner, and sort-of vampire, and initially think that the other two are normal. Also, there are two top-secret Japanese government organizations, one that fights aliens and another that fights the supernatural, that had an offscreen incident where they both mistook the other for enemies before sorting things out.
- Shifters of Flesh and Metal: Prior to encountering each other when investigating a quarry being used by the Yeerks, the Animorphs and Team Prime were totally in the dark about the other group. The final chapter reveals that this is standard policy for Unit E and by entension its parent organization, the Federal Bureau of Control, which deliberately keeps groups working with aliens unaware of each-other's existence.
- In There's More Magic Out There, a number of the students at Collège Françoise Dupont in Miraculous Ladybug are magical or supernatural beings, but before the events of the story, a vast majority of them don't know about the others. It's only when Juleka (a vampire) notices something odd about the fox coat that Alya (a selkie) owns that the magical students at the school begin making an effort to find each other and become a group of friends/allies. And this is completely separate from the mythology and magic surrounding the Miraculous, meaning they're completely unaware that two of their other classmates are superheroes, and the two superheroes are likewise unaware that werewolves, witches, and other such beings exist and that most of their acquaintances are among their ranks.
- In LuisJM's version of Transformers Prime Season 3, Team Prime, their allies, MECH, and the Decepticons were unaware of the existence of the Social Welfare Agency, who in turn didn't know that aliens existed and were already on Earth. This example has more justification than others - the two stories take place on separate continents, there are no Cybertronian relics in Italy, Team Prime only fights groups that directly oppose their actions, and the Social Welfare Agency does not try to root out terrorists from overseas. Funnily enough, the US Government did have evidence that the SWA existed, but never followed up on it because they had no reason to get involved.
- In Tim Burton's film Batman Returns, Bruce Wayne is dating Selina Kyle; he doesn't know she is Catwoman, and she doesn't know he is Batman. In the book of the movie, Selina even wishes that she'd met Bruce Wayne before she'd become Catwoman. They accidentally reveal their identities to each other when they repeat a bit of flirty banter from their costumed personas while in their civilian identities. They both realize simultaneously who the other person is and that they've blown their own cover as well.
- The Brothers (1979): The titular brothers are, respectively, a triad enforcer and a police inspector. They are actively trying to hunt each other down while preventing their mother from discovering the truth. It doesn't end well at all.
- Mr. & Mrs. Smith (2005), the movie where husband and wife discover each other's secrets: They're both assassins for hire, working for rival organizations. They find this out when they both get hired for the same job on opposite sides. The whole job is arranged by both rival groups to dispose of the problem their unwitting marriage caused.
- The Man Who Was Thursday: The protagonist is recruited as a secret agent so secret that none of the agents know who any of the other agents are. There are several moments later in the book when he discovers that some person he was suspicious of is actually one of his colleagues (and was, equally unknowing, just as suspicious of him).
- Monstrous Regiment: Polly pretends to be a boy called Ollie in order to join the army, then starts discovering one by one that the other members of her regiment are also girls disguised as boys...
- Louis' first introduction to Armand in Interview with the Vampire.
- Fairly common occurrence in the Deryni works set after the beginning of the persecutions, since many Deryni went into hiding one way or another to save their lives. A notable example occurs in The King's Justice when Bishop Arilan finds Jehana guilt-stricken after she warned Nigel of an assassination plot, knowledge she acquired thanks to her powers. First he tries to teach her through a couple of parables that she had an affirmative duty to reveal what she had learned, and when she retorts that he doesn't understand, he displays his Deryni aura to show her that he actually does.
- Harry Potter: Despite Harry having known about wizards and himself being a wizard for years, he was still surprised to find that Mrs Figg, one of his Privet Drive neighbors that he's known his entire life, has been in on the Masquerade the whole time and has also been tasked by Dumbledore to keep him safe.
- L.J. Smith's Night World series had a book called "Secret Vampire" that centered around vampire James Rasmussen and his mortal girlfriend Poppy. Poppy is terminally ill, so James reveals himself to her as a vampire and turns her in order to save her life. James has broken the second of two major laws in the Night World: Never tell a mortal about the Night World. (The first is "Never fall in love with a mortal" and he'd already broken that one.) At the end of the book, however, it turns out that, unbeknownst to both him and Poppy, she was really descended from witches and therefore was a member of the Night World, not a mortal.
- The Wheel of Time:
- This is standard procedure for the Black Ajah, an Ancient Conspiracy within the Aes Sedai who serve the Dark One. In order to prevent any Black Sister from having the knowledge needed to betray the entire organization, all Black Sisters except the top few are normally only ever given the identity of three other members. Most members do not even know who the next person up the chain of command is, much less who is at the head.
- When Osan'gar, one of the Dark One's foremost Forsaken servants, infiltrates The Chosen One Rand's forces, nobody outside the Forsaken is in the know — not even the Black Ajah sisters also infiltrating the group. Consequently, when he finally has an opportunity to assassinate Rand, he's promptly killed by a Black sister who thinks she's offing one of Rand's loyal bodyguards.
- Danilov Quintet: vampires have to hide themselves from human society. The protagonist discovers that the "mercenaries" his friend hired are in fact vampires. Later, he is shocked to find out one of the vampires isn't. So the villain could move about in the daylight ... Oh, Crap!. Furthermore, said character had fooled the other vampires into thinking he's one of them. It helped that the vampires weren't particularly strong.
- In The Secrets of the Immortal Nicholas Flamel, Josh and Sophie understandably try to cover up what's going on (the short version is that they're helping Nicholas Flamel stop people from bringing about the end of the world) from their parents and aunt, who they think are ordinary people, and who they fear will Go Mad from the Revelation. The fifth book reveals first that their aunt is a powerful immortal called She Who Watches, then that their parents are none other than Isis and Osiris.
- While most elements of the Masquerade avoid this in The Laundry Files, vampires are an exception as they're trying to remain secret even within it. As explained, if a vampire can recognize somebody else as a vampire, clearly the second vampire's very existence threatens to reveal vampires are real, and so the only reason why vampires communicate is if they haven't yet worked out their plans for killing each other. This fades rapidly after their introduction to the series (after the inevitable finally happens and a plan for killing another vampire involves threatening the Masquerade to force him to expose himself, the plan going bad on both sides).
- Batman (1966):
- In the third season, Batman and Robin did not know that Batgirl was Barbara Gordon any more than she knew who they were; Batgirl simply tended to show up whenever there was a crisis. Alfred learned her identity in one episode, however, but agreed to keep it secret.
- There was also a pair of cross-over episodes with The Green Hornet series. Bruce Wayne and Britt Reid originally met and socialized (they are both millionaire playboys, after all), with neither aware of the other's identity as a masked crimefighter. The villain of the episode - or rather, his Perky Female Minion - actually figures out that the two billionaires are also the two heroes but mixes up the secret identities (thinking Wayne is Green Hornet and Reid is Batman). When Batman proves this wrong, the idea is completely dismissed and the truth never occurs to anyone, including the heroes.
- Amazing Stories: "Moving Day": The episode featured the tale of a high-school-age boy whose parents revealed to him that a) they were actually alien scientists who came to Earth to study the "primitive culture" and b) their mission was over so they were returning home. The boy regretfully says goodbye to his High School sweetheart, lying to her about his dad getting a new job in a new city and them all moving away. On the spaceship, just before launch, he finds his girlfriend. Turns out her parents were also alien scientists, and that they are all going home.
- In Forever Knight, Nick's partner Tracy knows that vampires exist and knows that Vachon is a vampire. However, Vachon and Nick hide the fact that Nick is a vampire from her, and she doesn't find out until the last episode.
- In Kamen Rider 555, Takumi thinks Kiba is an okay guy but the Horse Orphenoch is a villain. Kiba thinks Takumi is an okay guy but Kamen Rider Faiz is a villain. Naturally, they learn each other's identities before they learn they are (or should be) on the same side. It doesn't help that Kusaka (ostensibly one of the good guys, but a Devil in Plain Sight and Manipulative Bastard) knows exactly what's going on and manipulates things to keep them at each other's throats, out of petty jealousy more than anything else.
- Star Trek: Enterprise has a brief example of this in one episode where the crew are disguised as locals while exploring a low-tech humanoid civilization on an inhabited world they've recently discovered, only to find out that the Malurians (another humanoid space-faring species) have already set up an underground base there and have an agent of their own living and working among the aliens disguised as a shopkeeper. When they go to confront him about this, they pull out a tricorder and inform him that their readings show he's not native to this planet. Pulling out some kind of scanner of his own, he takes a brief look at it and then replies "Neither are you."
- Buffy the Vampire Slayer
- In season 4, the Initiative are vaguely aware of the Slayer as a myth, but have no idea she a) really exists and b) is Buffy, while Buffy has no idea that her new boyfriend and one of her college professors are part of a military operation to do what destiny has decided is supposed to be her job.
- In season 7, Buffy has no idea that Principal Wood already knows who she is, or even that Wood knows of the existence of vampires. In turn, Wood is left unaware that the vampire in the basement of the high school is the same one who killed his mother.
- Wizards of Waverly Place: There have been several characters the Russos have met and have known to be muggles to them for quite a while before it was discovered that they were wizards or magical creatures as well. Notable examples are Stevie, Mason, and TJ.
- Chilling Adventures of Sabrina has one of these between Hilda and Doctor Cerberus, who's secretly possessed by an incubus and unaware Hilda is a witch. Once his secret comes out she's perfectly accepting, revealing her own and applying her knowledge to help him manage his "condition".
- Common occurrence in Chronicles of Darkness campaigns, due in part to the sheer number of masquerades that know next to nothing about each other. Most every gameline features a complex secret society of supernatural beings living hidden in human society — but those secret societies have little to no contact with each other; thus, vampires are only tangentially aware of the existence of mages, and both may be completely unaware of the Changeling freehold living in the same city as them, and they, in turn, might assume any vampires they meet are fellows changelings with an odd blood-drinking compulsion. Hunters and Prometheans (Frankenstein monsters) have this the worst — the former because they're humans who only know as much as they can figure out on their own about monsters, and thus get a lot of things wrong, and the latter because there are just so few of them Walking the Earth that one may go decades without encountering another of its own kind.
- Chronicles Of Darkness: The Contagion Chronicle, is a book about averting this by providing rules for crossovers between the many supernatural forces of the World Of Darkness; it focuses on an organization called the Sworn, comprised of all the different forces, who work together to combat a mysterious and destructive force called the Contagion.
- Scion has a similar problem by the simple expedient of every scion looking like a vanilla human until they reach godhood (or buy Epic Appearance). While a knack exists to detect your fellow godlings (and gods), there are few means to similarly detect Titanspawn or other creatures of Legend so this can crop up fairly often in play.
- Fate/stay night: Shirou Emiya and Rin Tohsaka are both shocked to learn the other is a Magus. In fact, Rin gets insulted that due to Shirou's lack of magical education, he had no idea the Tohsaka family is famous in the magical community, and that Magi living in Fuyuki City are supposed to register with the Tohsaka family.
- El Goonish Shive
- Quoth one high-ranked member of The Men in Black, "the accessibility of magic has always been the real secret." So there's a lot of magic users who have no clue about each other and lose time in otherwise trivial cases. Such as when a wizard's apprentice Noah was trying for days to investigate a magical incident, and since he couldn't tell what it's about and had zero diplomatic skills, he was forced to go the roundabout way through Elliot without telling him anything. Elliot himself being a full-fledged magic-user and knowing about the wizard but not Noah and working with another investigator connected to The Men in Black. By the time he got to his witness (yet another magic user who by this time had a good idea what's going on, but wasn't going to tell Noah anyway), the delay allowed the follow-up incident, which loudly finished off already damaged Masquerade.
- Later on, the The Secret Of Sam arc puts Grace at the crux of a similar situation. She knows that Sam is FTM transgender, has a magic mark that allows him to switch to male or back to female, and doesn't want to reveal this to Sarah (who he has only met either as or while pretending to be a biological male) for fear of her reaction. Grace also knows that Sarah loves transformation magic and is friends with multiple people who switch genders on a regular basis, but she can't tell Sam this without betraying her friends' secrets, and she can't ask for permission or explain the situation to Sarah without betraying Sam's secrets.
- Played for Comedy in the SCP Foundation tale "Everyone Knows": Turns out, the entire population of Earth is aware of the anomalies, sans one Jeremiah Wuthers (and even that is doubtful). The organizations have upheld The Masquerade simply because they have never correlated their membership numbers before.
- The Fairly OddParents!: In the episode "Fairy Fairy Quite Contrary", Timmy Turner notices that a rich classmate, Remy Buxaplenty, is at the center of some very suspicious events. Timmy decides to spy on him to figure out what's going on and discovers that he also has fairy godparents (well, a fair godparent). When Timmy asks Cosmo and Wanda why they didn't clue him in, the fairies reply that it's against Da Rules for fairies to tell their godchildren about other children with fairies. They have to figure it out on their own.
- The Batman: As in Returns, Bruce and Selina are attracted to each other in and out of costume. Unlike in the comics and other adaptations, neither ever finds out the other's alternate identity.
- The original Batman: The Animated Series had some of this going as well, as Bruce Wayne took a while to discover Selina Kyle's secret identity (while she never discovered his), while Dick Grayson (Robin and later Nightwing) and Barbara Gordon (Batgirl) also dated in college for quite some time before they figured out each other's secrets.
- Zorro: Generation Z: Diego and Maria have no idea of their counterparts being Zorro and the Scarlet Whip, until the last episode.
- Miraculous Ladybug: The two main characters Marinette and Adrien have no idea that the other is their superhero partner. This causes some complications in their romantic lives: Marinette loves Adrien, who thinks she's a good friend and has no idea how she feels. Cat Noir loves Ladybug, but she's endlessly annoyed by his constant flirting. The whole mess could easily be solved if they unmasked in front of each other, but their respective Kwamis have both firmly informed them that their secret identities must remain secret, even from each other. On top of all that, the two are constantly battling the minions of the evil Hawk Moth, who is in fact Adrien's father. The episodes Cat Blanc and Ephemeral hammer home the idea that if Adrien and Marinette were to reveal their identities to each other, the change in their behaviors both in and out of costume that would result would lead to Hawk Moth figuring everything out in short order (because Adrien lives with him) and using it against them.
- American Dragon: Jake Long: Jake is secretly a dragon and protector of New York City's magical community. His crush Rose is secretly Huntsgirl, a high-ranked member of an organization dedicated to killing magical creatures. This leads to situations like the two of them each ducking out of a study date with a paper-thin excuse so they can fight... each other. Jake is the first to realize what's going on after a fight ends with him realizing Rose and Huntsgirl share the same distinctive birth mark, and he begrudgingly reveals his identity to her in the season one finale. She breaks up with him, but they get back together early the following season to try and make it work.