Invisible to Adults

When in a story someone or something can only be seen by a select group of people, in an overwhelming amount of cases those people will be the children. Why? Possibly because Children Are Innocent, and they do not automatically disregard the unusual as impossible. This can lead to an Adults Are Useless scenario, where the child can lead their parents straight to the creature and even talk with it, but the adult simply cannot tell that the creature is there.

There is also the idea, closely related with the concept of the Masquerade, that all the fantasies one had as a child were in fact real, but people started denying them to be as they grew older. This is usually seen as a natural process that all people are subject to, although some are more seriously affected than others. Imaginary Friends and Santa Claus are typically presented as this. There is An Aesop about losing something important part of yourself with losing your inner child in stories that feature this idea. Occasionally you get a rare adult who is exempt from under the effect of this, usually because they have kept their childish demeanour and might be viewed as somewhat strange by normal society. Another grown-up who is affected by this but is still able to acknowledge the existence of the (to him) unseen world (out of faith or from second-hand experience) is also very common. Some coming of age stories present this as a tragic but inevitable process as the character is fully aware that this is happening to them, gradually losing their memory about how things used to be.

Subtrope to By the Eyes of the Blind. Sister trope to Invisible to Normals. Compare Adults Are Useless, and Children Are Special.

Anime and Manga

 * The forest spirits in My Neighbor Totoro
 * Zashiki Warashi in Urusei Yatsura.
 * Spirited Away might fall under this, although it's difficult to say for certain since the only human adults around are completely oblivious at first and later under a spell.
 * The entire world 'Nega Earth' is 'unavailable to adults in Element Hunters due to needing a particular portion of the brain which decays once they reach a certain age, and only shows up in a select few children. The adults are still far from useless though.
 * Only young children (for example, Amu's sister) or those who have Guardian Characters themselves seem able to see the Charas from Shugo Chara.
 * Not so true; Adults who had Shugo Charas (Nikaidou and possibly Tsukasa) are able to see them, and Yukari explains the reason she can see them as "Since I knew those things (Shugo Charas) existed, even I could see them".
 * When Taiki, Akari, Zenjiro and Shoutmon return to the human world midway through Digimon Xros Wars, only the trio are capable of seeing Shoutmon's flickering miniature manifestation; Taiki's mother can't, even when Shoutmon is trying to talk to her. When Tactimon turns up and Shoutmon becomes capable of existing properly in the real world to fight him, though, people are able to see them.

Comic Books

 * The angels and demons in PS238.
 * In Archie Comics, only adults can't see Santa's helpers, like Jingles the elf and Sugar Plum the fairy. In one story when Jingles stands in for Reggie at an Archies concert (He wears a costume so people can see him), he invites his fellow elves, leaving the adult portion of the audience wondering why the first few rows are empty.

Film

 * Angels in Wings of Desire.
 * In the Kirstie Alley tooth fairy movie Toothless, the tooth fairy can only be seen by children who have not yet lost all their baby teeth.
 * In The Polar Express, the bell from Santa's sleigh can only be heard to ring by people (mostly little kids) who sincerely believe in Santa.

Literature

 * Older Than Radio: Goethe's poem Der Erlkönig... or, according to an alternate interpretation, the child was hallucinating the Erlkönig as he was dying.
 * An Inversion, in the His Dark Materials trilogy, the Specters from Cittàgazze can only be seen by older people.
 * In Peter Pan, only kids can make it to Neverland.
 * In Mary Poppins, it's mentioned that very small children can see magical creatures, talk with animals, etc. They lose the ability around the same time their first teeth appear.
 * Aladdin's lamp, a poem by James Russel Lowell.
 * On the Discworld, Death can only be seen by those whose minds haven't been socially programmed to edit him out. This mostly includes children, who see him as the skeleton he is instead of a really thin man. And cats.
 * The same applies to the titular Wintersmith. Only children could hear him since adults "knew" that invisible creatures don't talk from out of thin air. The only other humans who could are the ones with pointy hats, who have trained themselves to see what's really there.
 * Only children can see the halfling creatures in Clifford Simak's "No World Of Their Own".
 * This becomes a minor plot point in the later part of Zilpha Keatley Snyder's The Changeling. Little Josie, who sees all kinds of things, says she saw and talked with the ghost mother Annabelle of the burnt-out house, who gave her a bunch of dried flowers.
 * In Stephen King's IT, only children can deal with "It" because they have not lost the power of belief.

Live Action TV

 * In the Buffy the Vampire Slayer episode "Killed by Death", Buffy thinks the Monster of the Week can only be seen by children.
 * Ghosts in Ghost Whisperer can sometimes be seen by children, as well as Melinda.
 * One episode of Charmed sees the sisters helping a young girl protect the fairy kingdom from trolls. Unfortunately, fairies can only be seen by children (or those who believe in them).
 * Back when Bob Saget hosted the show, America's Funniest Home Videos ran a fake trailer clip sent in by viewers, set up as an ad for a new sitcom, I Live With the Ghost of Abraham Lincoln; the basic premise of this "show" was that an average American family came to live with Abe Lincoln's ghost and the kids get into all kinds of wacky adventures with him because one of the twists is "Only kids can see him!"
 * In Quantum Leap only children and animals can see Sam's holographic guide Al.

Tabletop RPG

 * Any and all monsters in the Tabletop Game Little Fears.
 * Something similar applies to boogeymen from Dark Tales & Disturbing Legends, a Ravenloft supplement.
 * This trope is a major component of Changeling: The Dreaming. Childling characters have the most glamour, and therefore can easily perceive and interact with the chimera and other fantastical creatures around them. As a character ages, they slowly lose touch with their glamour, becoming trapped in the banality of the real world.

Video Games

 * The The Legend of Zelda the Minish Cap. In this case, it's the Minish/Picori people.
 * Trace Memory/Another Code plays this strait with ghosts, complete with the "some adults can see them" variant at the end of the first game with . Then again.
 * The Domovoi in Quest For Glory IV are small, hairy, imp-like creatures that live in the town buildings and bring good luck to the occupants. They can only be seen by children or special people, and with the latter it's only when they need help with something. The Domovoi you speak to specifically mention that you're obviously special somehow.

Web Comics

 * In the webcomic Weesh, only children can see the title character.

Web Original

 * The original stories surrounding Slender Man had him being only visible to the children he would eventually kidnap.
 * The imaginary friends from the Court of the Lost in Mirrorfall can't be seen parents, thanks to the ability to be selectively visible.
 * Candle Cove is a TV show in a creepypasta that adults only see as static.

Western Animation

 * Gazoo in The Flintstones can only really be seen by children, as well as Fred and Barney because they found him (although it's suggested that they have child-like intelligence).
 * Youngblood in Danny Phantom can only be seen by children. That doesn't include children who think they're adults.
 * A flashback episode of the second Teenage Mutant Ninja Turtles cartoon featured a skeletal demon who was able to do this thanks to an amulet he wore.
 * The Fairly Oddparents can be viewed by babies without triggering the need to go away forever.
 * Subverted in Foster's Home for Imaginary Friends - the friends remain visible to the whole world no matter what age.
 * Played with in Teen Titans. One of the baby heroes in the final season had a companion who may or may not have been an Imaginary Friend. It didn't become visible until Raven admitted she believed in it and it was no longer afraid of Raven. The eight foot tall nightmarish monster bear was shy.
 * In Winx Club when the fairies travel to Earth in one episode and take their pixies along, we learn that on Earth, only children and animals can see pixies.
 * Codename:Kids Next Door apparently has this in an extremely powerful 80 percent or such Masquerade. Adults are either useless idiots locked in a crazy fantastic illusion or villains almost all the time. Seriously, one time the candy pirate (Candy beard?) was driving his ship on land and instead of using freaking wheels, causes a deep crack in the ground by plowing through the street, causing houses to be crushed to pieces and the road broken. Imagine what kind of technology or magic can censor reality to that degree so people view a minor earthquake in precisely that matter.

Real Life

 * Real Life: There is an audio range that is primarily only heard by young people. You can read an article about it here.
 * Even if you have the hearing range to pick it up, sounds this high-pitched are still easy to overlook unless they're especially loud, because it sounds pretty much the same as tinnitus.
 * In an experiment put on by the Washington Post, on Jan. 12, 2007, Joshua Bell (if not the top living violinist certainly in the top five) took his 3.5 million dollar Stradivarius down to a Metro substation in Washington D.C. and played classical music as a busker. It was captured on film by hidden camera. Of the thousand people who passed him by, only seven adults sufficiently recognized that they were listening to something special and stopped to listen to him play (and only one recognized him). But on the film you can see most every child who hears his obvious skill brighten up, look around, and tug desperately at their parents who - having places to go and things to do - relentlessly bully them along. (He made $32 over about two hours, not counting $20 from the man who recognized him.)
 * People with the kinds of brains that make them hypersensitive (Autism spectrum, Asperger's, AD/HD) often notice things others can't. Imagine being a kid and being fully aware of the blink of fluorescent lights, or the itchiness of certain kinds of fabric, or that almost inaudible whine from electronics (which itself falls into the range of high-pitched sounds that can usually only be heard by young people), and being driven slowly insane by something no one else, least of all adults, seems to notice. Some people even have this well into adulthood, except that it's a little harmful when they were kids and being annoyed by something.
 * Children are reportedly more likely to have ESP abilities and see ghosts. As for whether this means that children are more psychically attuned, or that they have good imaginations...
 * Some cultures believe that fairies or ghosts can only be seen by children.