"We're given the greatest gift in the history of mankind. We're given this magic ball. And it says 'Imagine what you will and you can have it.' That's an extraordinary gift, but we're so primitive, we manifested the worst in us." —Norman Johnson, Sphere
This is the perennial excuse used by leaders of world-altering secret subcultures, and people with Secret Identities alike. It's a fairly reliable way for writers to engage Willing Suspension of Disbelief and to ensure Plausible Deniability.
The technologically-advanced global defense organization of the series won't have a massive impact on the day-to-day lives of all the mundanes, because they refuse to release any of their technology to the general public. They think people are bastards who will abuse the technology for war and profit once given access, or Luddites who will riot as soon as their incredible technology is unveiled, or just selfish pigs who all want to get their grubby hands on the shiny new tech (often to the exclusion of others). And of course, the very idea of letting the government get its hands on it is unthinkable.
One possible reason for a hero to maintain a Secret Identity or to ensure that everything remains Invisible to Normals (Other reasons include protecting the hero's family and that Celebrity Is Overrated).
At any rate, the show acknowledges that the fact that there's an alien invasion going on, a demon subculture, or Imported Alien Phlebotinum that should radically change the entire world. But folks with the power to keep this under wraps don't want the world to be radically changed, so they keep everything a secret.
Can lead to a Useless Superpowers scenario, where the heroes are hamstrung by the fact that they can't risk a crowd or Intrepid Reporter seeing them in action.
Increasingly subverted when it turns out that "The world is not ready" is just the official line — really, the people making the call just don't want to share... and will kill to keep their toys.
(Fridge Logic suggests that by just sitting on their knowledge even well-intentioned secret keepers ultimately work to prevent the world from ever becoming ready. This idea will usually either never occur to anybody or else be brought up once, handwaved away, and then never mentioned again.)
For practical reasons, it may be required to avoid changing society into a level which is hard to imagine for an audience, or to reduce the required amount of special effects. Also, there's little drama from story perspective if everyone can defend themselves from an alien menace. If you can instead put the safety of the entire word in the hands of one secret, tiny and underfunded hero team, the stakes get much higher.
However, the trope is not automatically unreasonable. It is possible to conceive of specific situations where the genie, in whatever form, could be put back into the bottle, and under the current circumstances such would be wise.
See also Masquerade, which covers the overall secret-keeping operation. Compare to You Are Not Ready, where its the protagonist trying to acquire something that can help them and only to be denied access for this reason. See also Science Is Bad where new technology is held back out of fear of misuse. See also Reed Richards Is Useless where the world remains unaffected for no apparent reason. Contrast with Just Think of the Potential when someone wants to expose what they've seen for the benefit of the world (and perhaps, naively failing to think of malicious potentials). Supertrope to Alien Non-Interference Clause.
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Subverted in Transformers: Cybertron. Optimus Prime refuses to throw off the masquerade and have the Autobots attempt to join with the humans in an alliance, even in the midst of a full-out Decepticon attack on Earth, thinking that humanity would feel betrayed when they found out alien robots had been hiding among them. Not so, it turns out. The Men in Black types that had earlier seemed threatening turn out to be a force for good, and play a role in turning the tide. It's a warm fuzzy moment for everyone but the Decepticons.
This is the main reason for The Masquerade in Mahou Sensei Negima!. Chao decided to get proactive and force the mages out into the open. Negi never really does come up with a reason that proves it would be a bad thing, but still fights her because he reasons that if she really had a good justification, she would need not hide anything.
Apparently this changes in the Time Skip to the sequel UQHolder but what lead to this change was not mentioned.
This is the government's supposed view of the Contractors in Darker Than Black. Ryuusei no Gemini showed that the world could be made ready relatively painlessly; the government agencies simply liked keeping their secret weapons.
Effectively averted, or at least ignored, in most Super Hero universes — the world is so filled with heroes, villains, aliens, mole men and so on that they're impossible to cover up. Of course, this leads to Reed Richards Is Useless.
Note that even in those universes most people still won't believe in magic, even with magic-using heroes operating openly; they are considered metahumans and liars.
One She-Hulk story from the 90s was based on the idea that the existence of aliens was not public knowledge, even after several alien invasions, Galactus standing on the Baxter Building more than once, Skrulls on TV, etc etc.
This actually got played straight in What If...? #9, where President Eisenhower orders the "Avengers" team of the 1950s to disband after their first mission - reasoning that the world simply isn't prepared to be protected by a talking gorilla and a wunderkind from Uranus.
Deconstructed in the comic series Planetary, in which an evil version of the Fantastic Four shows what happens when less than noble people use this excuse. They only claim the world isn't ready for technology so they can keep it all to themselves. They also actively kill and suppress anyone who tries to oust their secrets and take any super discoveries for "safe keeping".
In Marvel Comics, billions of years ago, the Watchers tried an experiment. They gave a primitive race the secrets of atomic power, which was an elementary science to the Watchers, but would allow the aliens to make huge advances to their society. The first advance they made was to build an interplanetary fleet with atomic warheads and go invade other planets. This resulted in other aliens killing the first aliens off in self-defense. The Watchers' reaction was to go "oops" and put their Alien Non-Interference Clause into effect.
In Concrete, the title character is abducted by mysterious aliens who transplant his brain into a 1200-pound stone-like body. When Concrete insists on living outside the confines of a government laboratory, The CIA concocts a story that he is the sole survivor of a failed super-soldier program, rather than admit to the existense of extra-terrestrials. Concrete agrees to play along, in exchange for his freedom.
Appears towards the end of Reflections. Celestia and Luna are discussing the future of ponykind. They could theoretically make everyone immortal star goddess like themselves, but they cannot because they are being punished for past crimes, as well for the simple fact that the ponies are very very very far from being ready to join them in eternity.
It's for this reason that Forbidden Planet's Dr. Morbius doesn't release Krell technology to the rest of humanity.
The main premise behind the films and animatedMen In Black series is the world not being ready to accept the existence of alien species, let alone be trusted with any of said aliens' advanced technology. Left unspoken is the issue that Earth is the galactic Truce Zone; its important that we be ready because if we aren't ready for the responsibility when the public learns, we'll probably cause a major galactic war or twelve.
James Edwards: Why the big secret? People are smart, they can handle it.
Agent K: A person is smart, people are dumb, panicky, dangerous animals and you know it. 1500 years ago, everybody knew the Earth was the center of the universe. 500 years ago, everybody knew the Earth was flat, and 15 minutes ago, you knew that people were alone on this planet. Imagine what you'll know tomorrow...
See also You Are Not Ready, since its used in the context of the humans wanting new weapons to help fight the bad guys.
Funny enough, in the sequel, Sam has a sizable chunk of Cybertronian science uploaded into his brain. Besides being laughed at for saying that Einstein was wrong, he can't even seem to find words for what he knows, lapsing into what sounds like a fax machine having a seizure, just when he's about to correct something.
In Chain Reaction, the Big Bad's justification for murderously suppressing the existence of clean fusion power is that the world economy would collapse. Unfortunately for him, the hero faxed copies of the blueprints to every conceivable location.
Morpheus in The Matrix explains that most people are not ready to be freed, as they've become dependent on the system. He goes on to explain that some are "so inured, so hopelessly dependent on the system, that they will fight to protect it."
Ms. Yutani and her henchmen at the end of Requiem, on the Predator gun they salvaged; "The world isn't ready for this technology. But it isn't for this world, is it, Ms. Yutani?"
Why the Tesseract is returned to Asgard at the end of The Avengers. The events of the film demonstrate that humans would misuse the Tesseract's power, but on top of that, the Earth simply can't deal with the kind of attention it would bring if it became widely known that humanity possessed the Tesseract.
Batman comes to this conclusion several times in The Dark Knight Saga. In the third movie, Alfred calls him out on the fact that he seems to apply this to everything. Sure, we can understand the world not being ready for a super-advanced sonar spy system or a fusion reactor that can be turned into a multi-megaton bomb, but you're not willing to give the police a wi-fi hacking device?
In Man of Steel, Clark starts off believing this as a result of Jonathan's advice.
In Orson Scott Card's Speaker for the Dead the laws of Starways Congress about contact between the new alien life reflect this trope. Ostensibly the laws were passed to "preserve the natural culture of the Pequeniños" but it's later realized that the laws are actually there so humans can stay on top of the technological race between species. So that when the Piggies actually can build a starship, and colonize other planets, they'll find that humans have already been there, done that. This is not entirely unjustified: in the sequels, when the Pequeniños do gain access to a Faster Than Light starship, there is a significant faction that wants to use it to travel to settled human worlds and infect them with The Plague, which is necessary to Pequeniño biology but unfailingly lethal to all forms of life not native to their planet.
In "The Adventure of the Sussex Vampire", Sherlock Holmes makes brief mention of a case which involved "the Giant Rat of Sumatra", and adds the world isn't ready for that story. Attempting to thwart this trope, numerous later authors have written fan-fic about the Rat.
In Top Secret by John Gardiner, the protagonist finds a way to cure world hunger forever by allowing people to photosynthesize. This technology is suppressed by the President on the grounds that it would lead to the collapse of the food preparation industry.
A Quantum Murder, a sci-fi murder mystery by Peter F. Hamilton, involves a murder commited via a laser mind-programming device (originally developed as a learning tool) and solved through a neurohormone that enables someone to look back in time. Alarmed by the implications of both devices, Julia Evans, the idealistic but powerful CEO of Event Horizon, arranges for the destruction of all records, and gives a generous job offer (of the accept-or-else kind) to the scientist who witnessed these events so she can keep an eye on him.
The antagonists of Roger Zelazny's Lord of Light use this as a justification for keeping their vast technology restricted to a tiny portion of the population. The protagonist calls them on it by asking why they've been actively quashing the spontaneous invention of technology.
Subverted in the Animorphs series. The Yeerks needed to keep their invasion secret because if humanity knew about it, they would overwhelm the invasion by sheer numbers. As Visser One once put it, "6 billion humans, all firing one bullet, missing almost 100 percent of the time, would wipe out the entire invasion." The Animorphs needed to keep their identities secret because if the Yeerks knew they were human, they could find them. Averted at the end of the series when the Big Bad of the series becomes Visser One and does take the invasion public—and almost wins.
Played straight in that the Andalites have their own version of the Prime Directive, "The Law of Seerow's Kindness", enacted when Prince Seerow tried to help another species, the Yeerks, out of their And I Must Scream existence. This bit the galaxy in the ass, big time. Resubverted when the only way to fix the mess is to break the rule.
And then subverted again in the final book according to Marco, who says that humanity doesn't panic at the revelation of extraterrestrial life. Or at least the side that wasn't trying to pull a mass Grand Theft Me invasion.
A major theme of Atlas Shrugged, though used unconventionally. First seen when a technology that allows electricity to be gathered from the atmosphere without any adverse side effects, pollution, or factories, lightweight and apparently easy to construct, is hidden by its inventor out of fear that the setting's collectivist governments would exploit that inventor and people like him. Later the same principle is applied to innovation and skilled labor in general, to greatly destructive effect.
In the first book of the Harry Potter series, Hagrid answers Harry's question about this with: "Everyone'd be wantin' magic solutions to their problems." (Hmm, is it still okay for wizards to acquire those magic solutions from other wizards? Right then.) The question is never raised again for the rest of the books. It is worth noting that magic is the only real defense against supernatural predators, some of which prey on humans. (An entire branch of the Ministry is devoting to keeping said predators from breaking The Masquerade.) And it makes the housework a lot easier.
Some have suggested, inferring from the implications of some Word of God statements, that the real reason is that the Ministry is terrified of what would happen if the Muggles ever did find out. Just imagine the practicality of modern technology enhanced to an unlimited degree with magic, Muggles would be unstoppable. So the wizarding world has cultivated condescending paternalism towards Muggles in their culture to conceal this underlying fear.
The fearful reactions of the Muggles are justified and demonstrated in the fifth book when Dudley, a Muggle teenager, gets attacked by a Dementor, the Harry Potter equivalent of a soul eater. Dudley is predictably mentally scarred by this and does a turnabout in treating Harry and accepting the existence of wizards... but only after being brought home from the attack in a shell-shocked-like state... and if Harry hadn't saved him he flat-out would have DIED.
The sixth book clearly states that the English Prime Minister, for one, has had The Masquerade revealed to him. This implies that other world leaders are also kept informed of the wizarding world.
In Ray Bradbury's 1953 short story The Flying Machine, a man invents the titular device in ancient China. The Emperor realizes that the machine could be used for war (such as for flying over the Great Wall of China), and has the inventor executed and the machine destroyed.
Hinted at in The Lord of the Rings, in which Gandalf observes that any device of an art deeper than one's own is dangerous. This doesn't go all the way to saying such devices should not be used, it's more like an observation and a call for caution, the reality of the risk is displayed by Denethor and Saruman.
In Quozl, stranded alien rabbit-people conclude that The World Is Not Ready for them to reveal their presence, so set about getting the world ready by working with human Secret Keepers to produce a children's television series about stranded (and harmless!) alien rabbit-people.
Subverted in that the Quozl are far more frightened of humans than humans have reason to be from them; the first encounter between a human and a Quozl resulted in the Quozl dying from a shotgun blast to the chest, while the aliens' own ray guns took multiple shots to put him down; they were designed for handling hostile fauna, and the Quozl never thought they'd face anything that could fire back. In fact, they were utterly shocked to discover that other sentient beings exist, considering the odds to be impossible. Despite being more primitive, humanity has frequently speculated about intelligent aliens; it never even occurred to Quozl, so they were less ready for us than we were for them.
Umberto Eco parodied this in a short story where a caveman professor invents the handaxe, but after realizing that the leaders want to use it against an another tribe, says that it should be destroyed.
Major plot point of A Connecticut Yankee in King Arthur's Court as Hank tries to introduce 19th-Century technology and democracy into the medieval era. It works for a time but only when he's there to teach them. The moment he has to leave the country for a family emergency, everything falls to pieces leading to a full blown war.
Becomes a major plot point in the My Teacher Is an Alien series. A vast alliance of aliens is terrified of earth because we are advancing quickly enough to soon discover interstellar travel, but still primitive enough to engage in war, meaning that when we learn the existence of the other races there could be trouble. Some aliens want to destroy us, some want to ignore us in the hope that we'll destroy ourselves, some want to sabotage our advance into space, and some want to take over the planet. In the end, the human Secret Keepers convince them to take a fifth option by sending alien teachers in disguise to peacefully guide humanity away from our savage behavior, so that someday we will be ready.
Live Action TV
Sometimes the reason that the Power Rangers must keep their identities a secret, even though the villains always know who they are.
There exists a healthy dollup of realpolitik on the U.S. government's side, too. There's been times when The Masquerade only hurt Earth's defense, as seen already in the first season when one Obstructive Bureaucrat was enough to get the Stargate program shut down because they couldn't go through proper channels to appeal. For all its levity, SG-1 poses a real philosophical dilemma over free exchange of information vs. national security.
Whether or not the world actually is ready is not as open to discussion as it should have been, given that in the Aschen timeline in "2010", the Stargate's existence was publicly revealed and people just treated it as another form of public transport. But the main-timeline SGC never learned anything about that timeline other than that they must not go to the Aschen homeworld, so they had no way of knowing this.
One late episode had a particularly interesting use of this trope: SG-1 visit another planet where they encounter a man who they end up telling that the Stargate (which was just a museum piece there, no-one knew that it did anything) can transport you to other planets. At the end of the episode, the alien government finds out about this, and, to the horror of SG-1's ally, declares that the world is not ready and begins their own Masquerade.
Alien technology is being slowly allowed to filter out into public use, however, "laundered" through various labs. Medical nanotechnology, for example, is more advanced in the Stargate verse than in real life due to things that have been learned from alien sources.
Knight Rider: The technology controlled by Knight Industries is kept a guarded secret lest it be used for ignoble purposes.
Played straight in The Lone Gunmen "Like Water For Octane" episode with the car that runs on water. The heroes themselves decide to suppress the technology because they felt humanity would make so many cars that engine oil would cause a greater environmental threat than gasoline usage would and that mankind wouldn't figure a way around that problem (besides, you know, recycling the stuff, like we do nowadays).
I thought it was to save the US economy from the collapse of the gasoline-based automotive industry.
A comparable discovery (broadcast power) is concealed by the heroes in Legacies, a Repairman Jack novel. Averted in that it's covered up because the late inventor's daughter, whom he'd molested, didn't want a bastard like him to be remembered as a great genius.
"Deathwalker" A notorious Dilgar war criminal has a medication that will give a person immortality. She later sadistically reveals that the essential components come from other beings of sapient species. Thus she intends to throw the various civilizations into murderous chaos in revenge. However, just as she is transported to Earth to give her medication and carry out her revenge, a Vorlon ship suddenly appears and destroys her ship, her and her medication. When the Vorlon ambassador, Kosh, is asked why that was done, he simply responds "You are not ready for immortality". Of course, it also denied everyone the opportunity to study the process and do research that could have eliminated that flaw. And considering how the Vorlons ended up treating the younger races, it could be a case of "we don't want you to have what makes us special."
Also the common excuse for those Minbari in the know not to reveal why they surrendered at the battle of the line. Or that Valen was in fact Jeffrey Sinclair. Humans would have dismissed the revelation as meaningless Minbari mysticism. It was the devastating consequences for the insular (and frankly quite racist) Minbari society that the Gray Council was worried about.
One episode of Star Trek: The Next Generation ends on this for an alien world with the government deciding that their people are not ready for space exploration or the knowledge of aliens because of the reaction of a cabinet member.
The Fourth Doctor once told the tale of the planet Minos. The Time Lords of Gallifrey, being a young race then, decided at help out the primitive planet Minos by instructing them in science and technology. The Minosans responded by kicking the Time Lords out at gunpoint then engaging in a nuclear war that reduced their homeworld to an asteroid belt. After that the Time Lords put their Prime Directive in place.
...That sounds kinda familiar... (see the Comics section)
In the Doctor Who Series Five two-parter 'The Hungry Earth'/'Cold Blood', a plan for the Silurians, the original reptilian inhabitants of the Earth, to re-emerge gets postponed for this reason. Considering that peace talks between them and the humans had broken down because of the murder of POWs and both sides claim equal right to ownership of the surface, this is probably one of the more justified examples. The Doctor also puts into motion a plan to make the world ready, by asking the humans to spread the message of the Silurians' return in 2,000 years.
In a more mundane example, an episode set in 1969 features an FBI agent thrown out of the service because of who he wants to marry. After he helps save the world, President Nixon concludes that she must be black and says he might be able to hep with the legal issue, since the US seems to be ready for mixed-race marriage. The ex-agent then corrects him, saying he is black. Nixon decides that landing on the moon is far enough.
Often mentioned in Torchwood as a justification for having to hide the existence of aliens or alien technology.
In Dollhouse this is the reason given for why their technology is so very misused. Not that, frankly, they seem particularly ready for the tech themselves.
As it turns out in Epitaph One they're absolutely right and the widespread use of their technology destroyed civilization. As Echo put it:
Kids playing with matches. And they burnt the house down.
In Friends to avoid hurting Joey's feelings, Rachel tells him that the world is not ready for him and his unisex bag.
Allie in Steven Spielberg's Taken miniseries was supposed to be a gift to humanity, a mixing of human and alien, but they decided the world wasn't ready for her.
In a Series 8 episode of Smallville, Clark publicly reveals himself to be "The Blur". After things initally go well for him, eventually however, his inability to be everywhere causes the public to descend upon him in an angry mob, blaming him for deaths he's failed to prevent. He retreats back to the farm, only for the military to arrive, attempting to apprehend him for study and experimentation. Clark is eventually forced to use a Legion Ring to go back in time to avert that reality, deciding that the world clearly wasn't ready for him just yet.
A major plot point on Farscape. The Ancient Crichton calls "Jack" (because he takes the appearance of his father) leaves hidden information on wormholes in Crichton's brain as a guide to help him find a way home, but doesn't outright tell him how to access it, specifically invoking this trope if Crichton is unable to figure it out on his own. The wormhole knowledge is soon hunted by both Scorpius and the Scarrans, who will stop at nothing to obtain it to use as a weapon. Later in the series, the Ancient named "Einstein" shows Crichton more overtly why wormhole technology should not be taken lightly. Finally Crichton himself demonstrates to Scorpius and Emperor Staleek in Peacekeeper Warsexactly why a species gaining access to wormhole technology before they're ready to use it responsibly is a very, verybad thing.
Crichton: OK, boy and girls, here are the rules. Find a penny, pick it up. Double it, you got two pennies. Double it again, four. Double it twenty-seven times and you've got a million dollars and the IRS all over your ass. Round and round and round it goes. Where it stops no one knows. But it all adds up...quick.
Played with in Ayreon's 01011001 when some of the Forevers argue that humanity isn't ready for advanced technology. They give humanity technology anyway - turns out humanity wasn't ready...
This trope inadvertently led to some of the conflicts of Final Fantasy IV. Some Lunarians wanted to simply observe the planet and leave humans alone; others, like KluYa, wanted to grant them the gift of advanced technology, producing the Tower of Babil, the Devil Road, and airships, but didn't take it further lest they adversely affect existing human civilizations. Dissidents like Zemus wanted to take over the planet wholesale, and giving the Puny Earthlings mechs and tanks puts a crimp in those plans.
Retroactively inverted in Mass Effect 2. Mordin will explain that this is what should have been done with the krogan when the salarians found them. Instead, they gave the krogans (who had achieved nuclear technology only to blast themselves back to the stone age) spacecraft and advanced weaponry, the reason being that krogan toughness, aggressiveness and sheer numbers were needed to combat the rachni. As a result of this "uplifting", the krogan expanded explosively with nothing to check their numbers or their aggression, necessitating a Depopulation Bomb that meant that only one out of every thousand pregnancies was born. Had the krogan naturally developed beyond their aggression, Mordin explains, this may not have been the case, and the krogan could have been prosperous.
This is a common theme in Mass Effect 2. Legion states this as the reason why the majority of the geth did not follow Sovereign. The Reaper was offering what they wanted - true unity - but they preferred to reach it on their own. Also invoked when discussing the fate of the Collector Base.
To say nothing of the Reapers, of course; one of the big reasons the Council denies their existence is to prevent the galaxy from descending into panic. Not that they'd need to cover it up in Mass Effect 3, of course...
At the conclusion of the College of Winterhold questline in Skyrim, the Psijic Order monks decide that Ancano's attempt to control the Eye of Magnus (nearly wiping Winterhold off the map in the process) is proof that world is not ready for the Eye of Magnus.
Present in one of the endings to Deus Ex, and heavily implied throughout the game. Everett literally asks - "Do you think they`re ready for this? After everything you`ve seen? Everything you`ve done?" That question gives JC pause, and he answers - "No. Not yet."
This is the justification the Brotherhood of Steel gives for their hoarding of pre-War tech in Fallout 3 and Fallout: New Vegas as well. Since mankind had already nuked the planet halfway to oblivion once already, the Brotherhood fears something similar happening down the road.
In STALKER: Shadow of Chernobyl, this is the reason that you are given for the true origin of the Zone being kept a secret by the C-Consciousness.
Devil Survivor and Shin Megami Tensei: Strange Journey both present this as a possibility in both cases and the equal possibility to avert it in the first case. Considering these games relate the story of massive demonic infestations and the horrifying depths humankind can sink to when backed into a corner, the protagonists for both games have fairly good cases going for them.
Tron 2.0 implies this trope at the end. Laser technology that can open up a whole new dimension? An entire civilization of artificial life forms? Human "Users" becoming PhysicalGods worshipped by those life forms? Unfortunately, Thorne and F-Con exploited all of it in the worst way possible, trying to enslave the Programs and have unlimited access to state secrets, global finance, and media to rule both worlds. Jet and Alan lock down the laser and the necessary algorithims to run it very tightly after they return to analog.
Jet:If anyone's crude, it's us we're not ready to exist here. Not yet, anyway.
The Invasion of monsters in the webcomic Parallel Dementia is kept secret, because the more people know the nightmares exist, the more there will appear.
In The Inexplicable Adventures of Bob!, when Jean takes offense at the alien Princess Voluptua's referring to the human race as "wildlife," Volly responds, "Jean, don't take it personally. Until you start interstellar space travel, everybody's wildlife."
In The Dragon Doctors —a world where magic is already known to exist— a spy on an exploration team tries to sabotage the discovery of the fountain of youth, fearing it will change the world for the worse. It doesn't, as we have seen already (this is a Backstory chapter).
In Wapsi Square, Monica is quite convinced that the world is not ready for the paranormal things that she deals with on a daily basis. The line itself first comes up after Shelly suggests using the Aztec god of alcohol to open a bar.
Actual real lightsabers, in the YouTube series Three In The Afternoon, and its sequel Six In The Morning. As Travis warns Jonathan and Corey, if they are spread throughout the world, people (especially children) cutting each other in half will become a regular occurrence, and much of the story is spent trying to stop renegade Lucasfilm execs from ruining civilization for a buck. After they seemingly succeed, George Lucas of course begins mass-marketing them anyway.
After his invention which opens a gateway between the the fictional world of Television and the real world causing hilarity to ensue Professor Bonkers feels this way about his own genius in The Garfield Show
In "X-Men: Evolution", the existence of the mutants is hidden because Professor X believes humans are unready to accept the mutants. When Magneto releases a Sentinel in public at the end of the second season, thus forcing the X-Men to use their powers out in public, the Professor's theory that mutants will not be accepted is proven right.
In Ben 10: Ultimate Alien "The Flame-keeper's Circle", Julie tries to convince Ben that wide-spread alien technology could benefit the Earth. Ben warns her that it could destroy Earth instead. It's happened before to other planets, and one of the reasons the Plumbers exist is to prevent it from happening again.
In Men In Black the series the above explanation is the reason Mi B stores so much alien hardware, the public is just not ready for it. They even date each item down to the year for when the world 'will' be ready.
Some episodes of the Super Mario World cartoon have the Marios try to introduce modern inventions and ideas to the local cave people. Depending on what it was, this trope would be in effect; For example, Mario gives them the wheel, but goes too far and builds them cars from Bamboo Technology. The resulting mess makes no one happy. Invoked in another episode where King Koopa introduces television (Actually Magikoopas in boxes) to brainwash the people.
Gravity Falls: When Dipper takes it upon himself to show the tourists of Gravity Falls some real magic, they end up traumatized.
To be fair to those tourists, said real magic consisted of a massive hemogoblin. If you looked into its eyes - which the tourists did - you lived your worst nightmares. It was basically an Eldritch Abomination.