Extra-Strength Masquerade

"We are assured as children that monsters don't exist. So even when someone sees a monster, he still doesn't remember seeing a monster. In his mind's eye he sees a "big dog" or a "large man" or a "blur at the edge of vision" -- anything except a creature he knows doesn't exist....The easy answer completely papers over what happened, and the world continues on, blissfully ordinary."

- D 20 Modern, Urban Arcana Campaign Setting

This is when a story has a Masquerade in place that, based on the events of the plot, should have been broken, but somehow isn't. Maybe a dragon terrorized the populace of Manhattan. Maybe aliens landed in London and had tea with the Queen. Or maybe the Sphinx came to life and led a mummy army against Cairo. Whatever the specifics may be, it seems like the world of the story should have become unmasqued, yet the general public seems as ignorant as ever.

Normally this sort of thing gets a Hand Wave about the Ancient Conspiracy or some other entity erasing everyone's memories of the event, passing the whole thing off as a hoax, or at least claiming people's Weirdness Censors take care of the Masquerade for them. Sometimes, though, we don't even get that. The Masquerade just seems to repair itself of its own accord. This is, of course, the most insulting way to handle it.

This has the additional benefit of lifting responsibility off the shoulders of the heroes; who now don't have to actively suppress anyone who knows the secret via methods above or passively promote ignorance by not warning Muggles about the supernatural beasties who want to control or kill them.

Anime and Manga

 * Digimon Adventure had digital monsters terrorizing Japan and, later, the rest of the world, for approximately 3 days. People could look up in the sky and see another world going on. Yet not only does the world return to normalcy within the next three years, nobody remembers any details about the events. They seem to recall that the events happened, but nobody seems to know exactly what. Either that, or their Weirdness Censors are set too high.
 * Digimon Savers manages to get away with a lot because DATS has memory erasing technology and enough pull to spin the media. Where it gets ridiculous is when an army of Digimon invades Japan. Hundreds of thousands, if not millions of people see the army of giant monsters with their own eyes. The only mention it ever gets is that the city is seen rebuilding in later episodes.
 * Mahou Sensei Negima takes full advantage of this, especially during Mahorafest. CGI handwaves notwithstanding, you'd think someone would catch on, what with the teleportation bullets and 100-foot-tall demon mecha. Then again, this is a school where the robotics club makes a full size robot T-Rex and a World Tree dominates the center of campus, so anything goes I guess.
 * Originally, it was stated that mages cast spells to make people stay away from magic and to instantly forget when they witness it. Negi casts such a spell when he tries to mindwipe Asuna in the beginning when she sees him (but she has Anti-Magic). However, when it became apparent that this would require a stupendous amount of mind-control (Black Magic according to the actual series!) and gray actions to enforce, they instead provided a (semi-) mundane reason of an extra-big festival event. It may be fantastic to the extreme, but it's non-magic fantastic, so the masquerade holds!
 * plan was to come up with a spell that would actually make people consider the idea by its merits, a world-wide forced recognition spell. How much of that Weirdness Censor is already there naturally and how much is created by the mages using similar (if smaller) magics is up to spirited debate. (And the plot itself has left Earth, so this is no longer an issue.)
 * Lampshaded when, in the Magical World, Rakan accidentally blows up a floating rock . Bystanders just say, "Are they shooting a movie?" Even magic citizens find some of the stuff going on unbelievable :)
 * Oh hey, there's Negi ! He must be helping the engineering department with a tech demo!
 * The Grail War events in Fate Stay Night are so tightly masqued that even though an uncommon frequency of deaths and comas are reported as 'chemical spills' and 'gas leaks', neither the news nor the Muggle characters reach the 'What the hell is going on?' hysteria of say, a virus with less than 5% propagation rate in the same community in Real Life, even when some of those Muggle characters are caught up in it themselves. Especially egregious in the visual novel's 'Heavens Feel' arc, when whole neighborhoods vanish. The novel and Fate\Zero justifies the effectiveness of the coverup as part of the Holy Church's operation, but the fact that no attempt is made to illustrate just how it's done makes it more of a Hand Wave.
 * In Heaven's Feel, the disappearances are most definitely not ignored. However, there is simply no evidence to point to the true cause. Similarly, in other routes, there is evidence to show that people are reacting to the events (such as the school having a curfew), even if they have no way of knowing why these events are happening.
 * This is what's probably happening in Axis Powers Hetalia, with the whole personified nations thing. It's a lot more obvious in the Movie, where there's an Alien Invasion going on. Apparently, NASA and every astronomer in the world were too busy looking at solar flares to notice the Pict showing up all of a sudden. And what makes it all the more crazy is that at least in Switzerland, Liechtenstein and, none of that's happening.
 * In quite good effect in Dragonball, where the general population forget about things like a Demon Lord taking over the world and alien invasions. On the other hand, they do remember Cell, but believing the words of the Fake Ultimate Hero believe that all of his superpowers were merely tricks pulled off with pre-arranged explosives and such and the events of the Majin Buu arc were erased from memory by the Dragon Balls.

Comic Books

 * In Marvel Comics' first Inferno Crisis Crossover, New York City was temporarily merged with a "Hell Dimension" - demons attacked people, inanimate things came to life, etc. After everything was restored to normal, people just assumed the whole thing had been a Shared Mass Hallucination!
 * Given the Fantasy Kitchen Sink that is the Marvel Universe, both explanations had a good chance of being right. From the perspective of your average person, it could easily have been a supervillain experimenting with hallucination inducing gas or something. The question is why they would believe the scientific option over the demonic one, despite having no real reason to do so.
 * Because it's easier, and less disturbing. Even in real life, the possibilities of creating such a gas sound realistic. New York merged with Hell, not so much.
 * In IDW's Transformers comics, Sixshot fought the Autobots in the American southeast, and the Machination had Laserbeak, Ravage, and the Dinobots running around causing havoc and fighting their Headmaster units. Cut to All Hail Megatron, and it only took a year for a crowd on the street in New York to think the Constructicons are part of a movie.

Fanfic

 * SG1/X-COM crossover XSGCOM plays with this. After battle of Antarctica (with humanity having two 303's and two Ha'Taks, plus a shitload of satelite weapons) and finaly having drone weapons launched X-COM decide to pull so unbelievable excuse, that it must be true: essentially they are claiming that Alien Invasion is a cover up for military-exercise-nearly-turned-WWIII. They also lie that governments have been breaching the disarmament of space. To normal journalist, governments trying to cover up major screw up by alien invasion sounds more possible than the other way around.
 * Note that this actually happened, sorta. The whole Roswell incident was actually a cover up for a top-secret early warning system for nuclear weapons.

Film

 * There are also examples where the Ancient Conspiracy did try to erase people's memories, but the coverup attempt is laughable. Really, do you think that in Men in Black 2 they managed to erase everyone's memory, considering that 1) it's doubtful everyone was looking at the Statue of Liberty, and 2) that doesn't erase photos?
 * Ghostbusters ends with a giant marshmallow man rampaging through the city and being destroyed by the title group in an impressive display of pyrotechnics. Ghost Busters II opens with the city still denying the existence of the paranormal and calling them frauds.
 * The end credits of the sequel show that the masquerade was broken, with the heroes getting a thank you from the city. Marshmallow man is one thing, having to haul the Statue of Liberty back to Liberty Island, presumably cleaning the mood slime out, and having to deal with the Titanic having finally come to port will do that.
 * Transformers: Revenge of the Fallen. Less than two years after a bunch of transforming Humongous Mecha had a giant droid deathmatch in the middle of a major city, everyone has forgotten and the bots are still hidden.
 * Lampshade is hung in the comic, where it's revealed the excuse was a runaway science experiment in unmanned drones. Sam can't believe people fell for it.
 * In The Sorcerers Apprentice, the main character's mentor explains that normal people must never know that magic exists. Later, an evil sorcerer creates a dragon that chases the main character through China Town. When police arrive citing reports of an actual dragon, the mentor, disguised as a fellow officer, says that it was just a bottle rocket hitting a paper dragon. Apparently that is enough to make the whole thing go away. Throughout the film, sorcerers throw powerful magic around with no one seeming to notice, although at one point a sorceress creates a flaming pentgram over New York and the hero's girlfriend literally can't see it, implying either that some magic is invisible to normals, or that normal minds refuse to accept it.
 * The upcoming film Apollo18 has the premise that there was a secret 18th mission to the moon. Aside from the enormous amounts of money, resources, specialized facilities, and trained personnel such a mission would require, this would necessarily require the government to cover up the launch of a Saturn V rocket. A Saturn V can be seen from hundreds of miles away during lift off, and is detectable by seismographs even further than that.
 * Inherent to The Matrix. Any and all evidence as to the Matrix's existence can be erased at will by the Machines, and even witnesses can be suborned.
 * Serial Killer Patrick Bateman of American Psycho confess his crimes to a lot of people but nobody seens to think he is being serious. Add to that the fact that proofs of his murders seen to vanish, which may be explained by Bateman being an Unreliable Narrator and obviously insane.

Literature

 * In Rick Riordan's Percy Jackson and The Olympians, this is under the control of the Mist, which keeps people from noticing. The gods themselves don't control it.
 * In Monster, most non-magical humans (called Incogs) are incapable of comprehending magic, so anything supernatural is automatically written off as something mundane; the few "light Cogs" that can partly comprehend it find themselves forgetting very quickly. In fact, this masquerade is so strong, it's started to bleed into the magical population, making it harder for true Cogs to cast spells and turning many magical creatures into endangered species. However, at the end of the novel, magic returns to power, allowing Incogs to witness the boom in supernatural activity without the weirdness censor.
 * The Dresden Files. Harry also spends a decent amount of time explaining why it works over the series.
 * This varies greatly depending on the events of the story. The villain in the first book could plausibly have been a drug dealer, and almost all the conflict could plausibly have been gang-related violence. Same for some later stories as well, where magical events just don't leave traces, or leave traces that could plausibly be mistaken for having mundane causes, and Harry points out real-world statistics which create lots of room for unexplained things. In other books, though, it just gets ridiculous, and Harry explains it all away in the closing narration just as easily as the magical drug dealing. Dinosaur bones found in a park for no apparent reason? College students must have played a prank. People saw a zombie tyrannosaur running through the street? It must have been mass hallucination caused by mold in a bad batch of bread!
 * ...And Harry agrees completely. He outright states that some of the shit they use to convince themselves that nothing supernatural is happening is less believable than "A private eye wizard resurrected the soul of a dinosaur, rode it through town, and used it to kick the ass of a zombie army."
 * What's noteworthy about this is that Harry, for the most part, really does not care about the Masquerade. While there are subjects he won't bring up (because he's forbidden, usually by way of the Wizards' Council or a risk of Speak of the Devil, or just lets someone/-thing stay secret out of professional courtesy), he's very open about his wizardry.
 * At one point, a vampire confronted by Harry believes himself safe because Dresden would never dare reveal himself to the world by openly attacking him at a crowded convention. In response, Harry points out that he's in the phonebook, under "wizards."
 * :ring: Harry Dresden! Yes, I'm really a wizard named Harry. No, I don't do parties. :click:
 * The young adult horror book series Strange Matter, about a town where strange supernatural events are constantly happening to the local kids, falls right into this trope with its first "Strange Forces" book; the ENTIRE TOWN is attacked by an army of monsters, including such crowded locations as the Mall at peak operating time, and the creatures are seen by hundreds of witnesses of all ages. Yet, later books seem to act as if the huge monster invasion never happened, and there are still people in town who are skeptical about the existence of the paranormal.
 * Justified in the Young Wizards series, since the wizards have a spell which can change the past by intentionally invoking a Reality Bleed from an Alternate Universe where the Masquerade was never broken.
 * In Fate Zero, the Church in conjunction with the Mage's Association have an extensive network reaching into the highest official levels to enforce the Masquerade. But the feeble excuses dismissing the events of the Grail War are only accepted because people want to believe them rather than the Eldritch Abomination summoned by Caster, or Berserker consuming and commandeering a state-of-the-art expensive jet fighter in mid-air.
 * Serial Killer Patrick Bateman of American Psycho confess his crimes to a lot of people but nobody seens to think he is being serious. Add to that the fact that proofs of his murders seen to vanish, which may be explained by Bateman being an Unreliable Narrator and obviously insane.

Live Action TV

 * Right from the beginning, Buffy the Vampire Slayer Handwaved the ease with which its Masquerade was kept by claiming that people would ignore or rationalize anything they weren't ready to believe. That worked okay for vampires, who might be able to pass as just really ugly psychopaths with a blood fetish. But when the Mayor turned into a giant demon snake during the middle of a graduation ceremony and did battle with the graduating class... well, even if people could pretend they never saw the giant snake, someone was bound to have been videotaping it.
 * Also note that the line about rationalisation (said by Giles) was in the second episode, after a vampire held several dozen people hostage, drained people one after the other, then exploded into a shower of dust after being staked by Buffy, and aside from the main characters absolutely no-one even comments on it. Extra Strength indeed.
 * It's heavily implied that many people in Sunnydale and elsewhere are perfectly aware of the supernatural, but there's a general unspoken agreement not to acknowledge it. Jonathan practically says as much when he gives Buffy the 'Class Protector' award.
 * It's not just Sunnydale's fine townsfolk. In one episode, musical guest Aimee Mann even comments how she "hates playing vampire towns", implying that a lot more people know what's going on (and that there are other "vampire towns"). This is finally subverted in the "Season 8" comic book continuation, when valley-girl vampire Harmony gets her own reality show on MTV.
 * Played literally in the 5th season, any humans who learned that Glory would instantly forget about it.
 * Lampshaded in season three in the episode "Gingerbread", where Joyce gathered a rally at city hall after two children were killed under suspect of cult activity  and she asked why the citizens continued to act so obliviously when either people went missing, or showed up dead with their blood drain, organs removed, or flayed, and that if they actually acted on said occurrences, it probably wouldn't happen so much. Alas, everything went back to status quo after the Monster of the Week was defeated.
 * In Season Four of Angel Los Angeles suffers fire raining down from the skies, an entire law firm being massacred and resurrected as zombies, a supernatural cloud blotting out the sun, allowing gangs of vampires to plunge the city into anarchy and slaughter, and thousands of people being Brainwashed by an Eldritch Abomination. But by Season Five, the public at large still doesn't seem to realize that the paranormal exists. How the heck they explained everything that happened the previous year is never revealed. At least Jasmine's "message" never made it much past LA, as she was defeated during her first global broadcast.
 * In the "Season 6" comics,
 * In Heroes, it's often a major plot point that the superpowered characters keep their existence a secret from most of humanity. However, at the end of Season 1, Peter gave off a giant nuclear blast in the skies above New York City. While that doesn't immediately lead to the conclusion that superpowers exist, you'd figure people would demand some sort of explanation for what caused that burst of radiation, but no one, including the show's resident The Men in Black, seems concerned about that.
 * Not to mention that during the period when Elle couldn't control her power, there were electric bolts running over her skin the whole time. She took a plane flight with tonnes of other people and not one of them noticed.
 * In the Volume Five finale, which ended up as the series finale,
 * Doctor Who: No matter how many aliens invaded Earth, people just never seemed to catch on. The series had started hanging lampshades on it by the end of the original run: for instance, in "Remembrance of the Daleks" Ace complains that if Daleks had invaded London in 1963 she'd have heard about it when she was growing up in the 1980s; the Doctor responds by pointing out several other alien invasions she never heard about, remarking that the human species "has an amazing capacity for self-deception". We see this explicitly in action at the end of the new-series episode "World War Three", where people are already beginning to convince themselves that the latest alien invasion was just a hoax or a publicity stunt.
 * The Masquerade was supposed to have been officially broken in "The Christmas Invasion", but it took a while to set in - it isn't until "Love and Monsters" and "Army of Ghosts" that people finally begin to talk about aliens as a fact of life. Later episodes of the new series show it beginning to sink in at last; in the 2007 Christmas special, the population of London has become Genre Savvy enough to evacuate at Christmas in case something bad and alien-related happens again.
 * There are still people sticking their heads in holes and pretending the masquerade still exists - but in a bit of a turnaround, most people who deny aliens exist in the past several episodes are treated with the same sort of eye rolling and patronization as people who insist aliens do exist in Real Life.
 * And then new series five repaired the masquerade again by having those bits of human history simply erased. It didn't last though, those events were restored by the end of the season, and the masquerade is once again broken.
 * This also somehow carried over into spinoff series Torchwood. The residents of Cardiff seem to be in denial about the existence of aliens, despite Cardiff being a part of the same country as London (depending on who you ask). Initially, Gwen and her boyfriend Rhys (representative of Cardiff's populace generally) believe that it is an inversion of a Gas Leak Coverup. Which is to say that someone actually used hallucinogenic gas on the public to cause them to believe that fantastical events occurred in order to cover up mundane skullduggery.
 * Stargate SG-1 is not quite so bad, but has its moments. They had a building teleported into space, fired nuclear missiles in orbit, and realistically, all the alien fleets attacking the Earth could not possibly go unnoticed by astronomers. There was one episode where they made everyone who witnessed an incident sign non-disclosure agreements.
 * The USS Nimitz, and its carrier group, are destroyed by Anubis's fleet, doubtless causing thousands of deaths. Worldwide communications are knocked out, and a giant swarm of glowing drones destroys a huge alien fleet in orbit of Earth. One hell of a meteor shower!
 * Stargate Atlantis mostly avoids this, being set in another galaxy. Except the Grand Finale, where a battle between a Floating Island the size of Manhattan and a ship of similar size goes completely unnoticed. Even when the ship is destroyed from inside by a nuke. People do notice when the survivor falls into the atmosphere, but the fact that it's the Lost City of Atlantis is conveniently obscured by the re-entry fireball. Even more convenient is the fact that everbody in the Western Hemisphere was apparently looking away when the fireball dispersed, leaving time to use their Invisibility Cloak... and nobody realized that an object that large should have done massive damage on impact, unless it was powered and decelerated on its own.
 * Power Rangers normally averts this trope, to the point where Bulk and Skull were described as having a mindset ideal for police work, in Angel Grove, because they were obsessed with monsters, but it is played straight a few times.
 * In Power Rangers Ninja Storm, only Dustin initially believes that Power Rangers are real and not just something out of the comic books. Apparently, the rest of the cast totally missed ten seasons worth of Monster of the Week attacks, and the time the Earth was briefly taken over by Astronema.
 * It's suspected that this is Continuity Drift, with the season originally meant to be set in a completely seperate universe from the other Power Rangers shows, something also supported by the lack of a team-up episode with the previous seasons team like all other new teams until then had done. Unfortunately, this conceit was wrecked when the Ninja Storm Rangers appeared in the following season, which is firmly set in the same universe as the others, given the presence of Tommy.
 * In the middle of Power Rangers Lightspeed Rescue, a girl who saw a monster is assured by a woman that monsters do not exist. (Yes, this is in the city that is the main setting of the series, the one that's being constantly targeted by monsters.)
 * Linkara while reviewing the season dubbed her "The Stupidest Person in Power Rangers History", especially when you consider the fact that the Earth was conquered just 2 years ago...
 * Supernatural is an odd case what with All Myths Are True, but even in a word that has gone through apocalypse, people still surprised by a mere vampire.

Tabletop RPG
"While mere mortals will screw up a Wonder something fierce, there is no cosmic principle or conspiracy at work that relates to Wonders or Inspiration. There is nothing in a Wonder that "clouds men's minds" or that will cause them to grow confused. Wonders show up fine on cameras and videos. There are no vast conspiracies to hide the truth from regular mortals. In fact, the vastest conspiracy out there, Lemuria, wants to make regular mortals aware of their brilliance.
 * The Urban Arcana setting of d20 Modern explains the inability of most people to see the supernatural by saying that even when people notice the bizarre, their minds simply explain it away. This is apparently strong enough to explain away events such as goblin street gangs, spirit infestations, and the sun not rising after a full moon. (All of which are listed as adventure seeds.)
 * Specifically, creatures of shadow will always be seen by most mortals as their nearest mundane equivalent. With no effort at all a goblin may look like a child and a bugbear like a linebacker. Most notably, is the Illithid (Squid Men) business man. Basically a full-powered environmental Weirdness Censor.
 * Also noteworthy is that it doesn't seem to be just a trick of the mind, as even people that believe in the supernatural and have actively fought it can't always see through it. The 'partially aware' can see the supernatural, but the more out there it is, the more likly they need it pointed out to them first by a 'fully aware'. They can see the more relatively mundane things like a goblin or a zombie just fine, but a psychic squidman or a demon made out of a swarm of maggots? Not so much. It's worth noting that creatures of Shadow, even the unintelligent ones, seem to instinctively know just how 'aware' a person is.
 * In addition, when a creature of Shadow dies, its body dissolves, leaving behind no evidence.
 * Noteworthy in the Old World of Darkness, especially Werewolf: The Apocalypse where rampaging and crazy wolfmen are just a fact of life. In most cases, this is canon -- said werewolves inspire a horrible and mind-numbing panic in normal humans, the vampires are secretive and have fingers everywhere, and the mage willing to try magic on television will just blow his own head off in a way that everyone believes is natural. Still, the canon events alone seem like they'd have made more people aware, never mind what a careless GM can cause.
 * The most clear example of Extra Strength Masquerade is found in a Splat where a Son of Ether descends over the World Science Fair in early 20th-century Paris with a fleet of robot-guided airships. He declares world dominion by right of higher knowledge. Airplanes sent up to fight him are useless, but eventually the Technocracy manages to drive him away by using flying Mark robots. The breach in the Masquerade is total, but so is the Technocracy's propaganda machine, working around the clock for years to eradicate all memory of the incident.
 * Vampires' Extra Strength Masquerade is backed by them having the most thorough organization for maintaining the Masquerade of all supernatural splats, an organization which at least claims every vampire in existence as a member, and by said Masquerade also being the lynchpin of their political maneuverings. Individual vampires try to avoid even the most trivial Masquerade breach for fear that their enemies might use it to bring them down, young vampires try to curry favor with their elders and eliminate the competition by cleaning up everyone else's breaches, and every elder vampire who lasts long enough to become an elder fervently agrees with maintaining the status quo. Also, entire campaigns can be made out of playing Archons responsible for cleaning up after neonates gone Michael Bay.
 * And notably averted in fan game Genius: The Transgression:

The nature of Inspiration, instead, remains hidden because Wonders are not repeatable and testable. A regular scientist who handles a Wonder will break it, and if they don't break it, they're already well on their way to becoming a Genius themself (or at least a Beholden). The only results, then, are that a mortal will mess up the Wonder (possibly killing themself in the process) or will at least turn into a Beholden or Genius and join the ranks of the Inspired, which in turn insulates them further from regular people."


 * In the story at the beginning of Hunter: The Reckoning, one of the characters tries to reveal himself to the world on Chicago's WGN News by creating a magic sword and destroying a chair with it. Unfortunately, the sword is invisible to the television cameras, and later on several illusionists go on the news showing how his "trick" was done.
 * The New World of Darkness (of which Genius is part) has every supernatural race contain at least one subgroup with the job description "Hide the evidence". However, when the masquerade does slip... well, then you have the Hunters. Network Zero, in particular, is devoted to breaking the masquerade.
 * Also keep in mind that, in the New World of Darkness, Muggles DO start to believe in the supernatural when they see monsters come around their backyards. However, when those enlightened muggles try to make their discoveries public, they are viewed as cranks and conspiracy theorists by the world at large. Add to that the fact that both the Government Conspiracy and the various non-human Masquerades systematically erase the evidence, and it's easy to see why people remain largely unaware. The Union is a good example of such enlightened muggles.
 * Then there are the powers/side effects of said powers that automatically lead to an Extra Strength Masquerade. As mentioned above, Werewolf: The Apocalypse has the Delirium, where the vast majority of humans who see werewolves in their war form get overwhelmed with ancestral memories of fear and dread and automatically blank out memories of what they experienced; this carries over into Werewolf: The Forsaken as Lunacy, a blessing from the werewolves' patron goddess. Changeling: The Dreaming, meanwhile, has The Mists, a side effect of widespread Banality where any observation of fae magic will usually slip out of a mortal witness's mind by the end of the scene. Mage: The Awakening, in addition to Paradox (which targets vulgar magic as it goes off), has Disbelief, which means anything obviously magical (like, say, a rampaging fire elemental crafted by an Obrimos) will rapidly degrade under observation by Sleepers.
 * In the more technologically-advanced domains of Ravenloft, many natives doubt the existence of supernatural threats that are readily acknowledged in distant backwater domains. Justified in that the Dark Powers create each domain to reflect its resident darklord's prejudices and biases, so if Lamordians don't believe in magic or Dementlieuse assume that sahuagin are just fishermen's tall tales, blame the local darklord's own skepticism.
 * The Palladium Books game  Nightspawn Nightbane for the most part is a normal Masquerade, but the event that started it all was literally seen by everyone on Earth. On March 6th, 2000, also known as Dark Day, the entire Earth seemed to be cut off from the Cosmos. No sun, no moon, no stars, for 24 hours. To those with knowledge of the supernatural, it was the day evil beings from parallel dimension breached the wall between the two worlds and began a covert operation to control the whole world. To everyone else, it was a freak occurrence they'd all rather forget about. A number of excuses for the event were put forth, and people accept that there must have been some natural explanation, regardless of how flimsy it is.
 * Cthulhu Tech has a Masquerade that, by all logic, should have been shattered into little pieces, but somehow the very existence of the Aeon War and the Eldritch Society side plot are kept secret from the people of the NEG-controlled Earth, thanks to at least three conspiracies working as The Men in Black. Attempting to bust things open will just get the entire NEG dropped on your head without actually breaking through the censorship.

Video Games

 * In Persona 3, The Masquerade keeps the population of Iwatodai from ever learning of the Dark Hour, the existence of Shadows, and that a select few can summon their Personas during the former to battle the latter. This is helped by the fact that, during the Dark Hour, most people are transmogrified into coffins... and those who aren't, freak out at the occurrence, are preyed upon by Shadows, and are consumed from the inside, ending up as shambling husks (a condition known to the public as "Apathy Syndrome"). However, every time the heroes defeat a Master of Shadows, its victims return to normal, and they lose all recollection of the Dark Hour they witnessed. Especially egregious, and even worse in.
 * Explained by a bad ending in which the heroes willingly let their minds be erased of every Dark Hour they lived. If they can be erased, then they probably were of everyone else.
 * Doesn't the game explicitly state at one point that only people who have mastered their Persona can remember the events of the Dark Hour, even if they both experience it and survive? I can't recall the exact quote, but it was something to the effect of, "She doesn't have the power like us, she won't remember any of this." They seem to be subconsciously aware that something happened, but they can't recall any details and most will just assume they were dreaming.
 * Destroy All Humans. You can rampage the city, either on foot or by flying saucer, and the public will still have no idea aliens exist. Any destruction you cause is blamed on Dirty Commies.
 * In Metal Gear Solid 2, a Humongous Mecha (and I'm stressing the word humongous here) goes crashing straight into good old Manhattan. Not that anybody cares. You see people passing by, casually heading for their workplace, not even turning their heads to see that a freakin' MECHA BATTLESHIP nearly crushed their homes. Seriously.
 * To be fair, they ARE New Yorkers.
 * To be more fair, this is far from the weirdest thing to happen in that ending.
 * The end of Vampire: The Masquerade Bloodlines has Since the game is ending at that point you never get told how anyone managed to cover that whopper up, but one can imagine The Camarilla are none too pleased at the perpetrator.
 * Considering that white-wolf's Canon says that a event heralding the apocolypse that breaks the masquerade worldwide happens soon after, the chiropteran behemoth breaking LA's masquerade is moot.

Web Comics

 * Megatokyo has some confusing relations with this trope, as better explained under Weirdness Censor.
 * Narbonic lampshades and explains this in the third strip here.

Western Animation

 * Kenny from South Park, yet no one else knows this even though he has died repeatedly in front of his best friends. He even goes so far as to commit suicide, telling everyone to "remember this time." Still, to this day, no one else knows about his powers. but it's not explained in detail.
 * Gargoyles' masquerade could be surprisingly resilient when the creators wanted it to be: after a spell turns most of Manhattan's population into stone for two consecutive nights, said population lets it go with a shrug. While there's a scene where the people are understandably frightened at the prospect of having lost a night, nothing comes of it. Nobody outside of Manhattan seems to notice the largest city in America shut down completely either.
 * That one's especially egregious, if you know that much of Manhattan's subway system would flood within a matter of hours if nobody was there to operate its pumping stations.
 * There's also the fact that Demona shattered some people while they were turned to stone yet no one questioned were they went.
 * In "The Mirror", all of Manhattan's population is turned into Gargoyles for several hours. Of course they don't notice a difference due to the spell, but apparently none of them photographed themselves or drove outside the island during this time. What's more, the director's online commentary notes that the transformation destroyed their shoes and the re-transformation doesn't return them. Nobody thinks much is odd about suddenly losing their footwear.
 * And somehow, Oberon putting the whole city to sleep in the middle of whatever they were doing ("The Gathering") does not result in thousands of deaths.
 * Likewise, the statue incident above should've led to situations like, say, a petrified bus driver's foot being immovably locked onto the accelerator...
 * Puck Did It.
 * This appears to be the case in Codename Kids Next Door, assuming there even is a Masquerade at all. (It's complicated.) All the adults who aren't villains seem to be completely unaware of what their children are doing or that evil adults are running around causing havoc, despite the fact that both sides' Humongous Mecha fight each other in the streets. The Men in Black would kill to have citizens who could deny the evidence of their own eyes!
 * As in the Men in Black example in the film folder, a similar tactic was used in an episode of the Animated Adaptation, but with the Empire State Building in the place of the Statue of Liberty. Another episode shows that every traffic light in NYC has a built-in neuralyzer. In these cases, they at least made a public announcement asking everyone to look at the neuralyzers first.
 * The Grand Finale had an all-out Alien Invasion, forcing The Men in Black to reveal themselves to the world in order to join forces with the authorities. They combine modern fighter jets and alien weapons to beat back the attackers. The Men in Black are hailed as saviors, and the award ceremony is broadcasted to the entire world (or so they say). One of them takes out a neuralizer and points it at the camera, wiping out everybody's memory of what happened. But what about people who don't watch TV?
 * They become conspiracy theorists and crazies.

Real Life

 * Whether or not there are any Extra Strength Masquerades in the Real World is debatable, depending on one's personal level of paranoia. There is, however, a rich tapestry of fringe hypotheses in which Masquerades could hide. Western academia and law enforcement are skeptical to say the least, arguing that extraordinary claims require extraordinary evidence. Many of our credentialed intelligentsia have been defamed and discredited for giving mere consideration to fringe theories, often in fields at most tangentially related to the one they study.
 * The Tlatelolco Massacre. Inverted, since back then the population never knew that 250 people were killed. Now everybody with internet access knows what happened (few people defend the then-president and then-secretary of State by calling the students communists).
 * This is a popular theory about why uninvolved civilians in Germany and Nazi-occupied territory allowed the shoah/holocaust to take place. The theory goes that, given that hordes of people were being murdered, and that death and slave labour camps were all over the place, a lot of civilians must have known. They just pretended not to due to racism, the personal tragedies and stresses of being involved in war, how unbelievably horrific the atrocities were and how dangerous it would have been to look too deeply into the matter ( giving that they were living in a fascist dictatorship). If this was the case, then the holocaust was everybody's 'open secret".
 * People in Nazi-occupied places really preferred to be not occupied but were unable to change this, public executions were commons etc. (Photo from mass execution of Poles in Piaśnica (Groß Piasnitz) in the Darzlubska Wilderness (Polish Pomerania) conducted by nazi Germans)