Not-So-Imaginary Friend

""Hello everyone! I'm Amy's imaginary friend. But I came anyway.""

- The Doctor

Unlike an Imaginary Friend, a Not So Imaginary Friend is real, but due to a pile-up of coincidences, mystical restrictions, an explicit or implied Weirdness Censor, or deliberate evasiveness on this character's part, he remains unseen by others.

Generally, by the end of the episode, this character's existence has been proven and the person seeing it gets vindicated, but not always.

This plot is also referred to as "The Singing Frog", after One Froggy Evening, the famous Looney Tunes cartoon in which a man cannot convince anyone that a frog he has found can sing and dance, and ends up broke and homeless because of it.

Compare with It Was Here I Swear. See also Cassandra Truth, Ignored Expert. If the character(s) seeing this character are not believed because they've lied in the past, it's Crying Wolf. Sometimes this character will be Mistaken for An Imposter.

The Other Wiki has an entry on the Martha Mitchell effect, cases where an individual is misdiagnosed over hallucinations that were, in fact, real.

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 * If Mr. Giggles ever asks you for some cheese, say yes.

Anime & Manga
"Deus: "I'm a god. Why can't I live in your imagination?""
 * As is its fashion, Elfen Lied provides a particularly brutal example between Nana and Cute Mute Nyuu: Nana knows that Nyuu has an alternate personality called Lucy who is an Ax Crazy mass murderer, but no-one else believes her.
 * Deus Ex Machina from Mirai Nikki is introduced as such, but we very quickly learn that this is not the case, he is actually God, and he's been preparing a rather sick game.


 * In Higurashi no Naku Koro Ni, when Rika Furude was very young, she had a friend only she could see named Hanyuu who gave her knowledge of things like cooking and cleaning. So she was never seen to learn them. Given that Rika was the daughter of the village priest and thought to be the reincarnation of Oyashiro-sama, the local deity, the villagers quickly decide this is evidence of the reincarnation and nearly worship her.
 * The Shinigami in Death Note are a rare example of an actively hidden Non-Imaginary Friend, though most of the cast knows about them by the end.
 * Inverted in Manga/King of Thorn.
 * An inversion happens in the Sailor Moon R movie. Mamoru was convinced the alien he saw upon waking up in the hospital, Fiore was only an imaginary friend.
 * Kyubey of Puella Magi Madoka Magica is such that only magical girls (and those who have the potential to be such) can see him.
 * Fridge Horror: Kyubey has strong telepathic powers that enable him to talk to people from far away. He holds conversations with people who are not themselves able to talk telepathically which means he is reading their minds. Kyubey's Invisible to Normalsness probably involves manipulating people's minds into not noticing him.
 * Maromi from Paranoia Agent. Or is it?
 * England and his magical friends from "Axis Powers Hetalia"- nobody else, save for Norway perhaps, can see them, so they think he's delusional when they catch him talking to or about them, but the fact that he saw a tengu and a youkai when he was at Japan's house as well proves that Flying Mint Bunny and the others have to be real as well.
 * Puck the elf fills this role in Berserk. Since normal people who have never experienced the supernatural or who are devout followers of the Holy See religion can't see supernatural creatures, anyone who encounters Guts often wonder who the hell he is talking to over his shoulder.

Comics

 * Prior to the Onslaught saga, young Franklin Richards was visited by a so-called "imaginary friend" by the name of Charlie. When "Charlie" telekinetically causes Franklin to drop a glass of milk, he was chided by his mother for it. When Franklin tried to blame it on Charlie, Invisible Woman replies "Your invisible friend?" Of course, "Charlie" wound up being a projection of Onslaught trying to manipulate the most potentially powerful human on Earth.
 * This is especially stupid on Sue's part since she's invisible half the time.
 * Blue Monday features Shamus, a six foot, smelly, perverted weasel. Bleu's best friend Clover calls her crazy due to Bleu blaming many things on "Shamus". Fast forward a series and it turns out Clover could see and even talk to Shamus all along, she was just giving Bleu shit.
 * In one comic Donald Duck was sent to the asylum because he was claiming that he's friends with Easter Bunny, whom only he could see. In the asylum other patients started to see Rabbit as well and he was apparently curing them from their own issues. It was hinted that Bunny could be Real After All (we never seen more than his shadow).
 * Another comic had an imaginary fiend which was the incarnation of a common cold. That could counter cold remedies by taking remedies of his own.
 * The Newsboys Legion member "Gabby" was friends with a huge furniture-eating pink monster named Angry Charlie, but the other kids didn't believe about Charlie (who helped Guardian and the boys, but always out of sight). Charlie revealed himself when he had to help against Boss Moxie and the forces of Apokolips.
 * Hobbes, of Calvin and Hobbes, is often interpreted as one of these. However, Bill Watterson always made a point of insisting that neither Calvin (who sees him as a living, breathing creature) nor the other human characters (who see him as a stuffed toy) necessarily has the "true" perspective.
 * One plot involved Calvin and Hobbes time traveling shortly into the future, where Calvin should have finished a homework assignment, so he could travel back with it without having done it himself. (Not that that makes sense anyway, but just go with it.) While Calvin and his time-duplicate argue over who should do the assignment, Hobbes and his time duplicate write it together, and use it to make fun of Calvin and his plan. Calvin, without reading it, turns in the assignment, which was noted as being different and better from Calvin's usual style, and capable of talking a joke about himself, which Calvin is not.
 * Mr. O'Malley, the diminutive, cigar-chomping fairy godfather in Crockett Johnson's Barnaby, was, in spite of the best efforts of Barnaby and his friend Jane, only ever known to exist to the two of them. Numerous potential introductions are ruined by Barnaby's parents looking away at just the wrong moment or leaving the room as he entered, and the two steadfastly refused to believe O'Malley existed in spite of rapidly mounting evidence to the contrary. The strip ended with Barnaby reaching his sixth birthday, forcing Mr. O'Malley to disappear from his life.
 * In Curtis, there's Gunk's pet "Flyspeck Island chameleon", who's constantly breaking things and creating other types of havoc and getting Curtis in trouble with his parents, who assume he's making the creature up. It doesn't help that the chameleon has the power of invisibility.
 * The Family Circus has occasional appearances by invisible, troublemaking ghosts or gremlins with names like "Not Me" and "Ida Know". While they're obviously meant to be a Visual Pun on the time-honored tendency of children to deny responsibility when confronted with their misdeeds, it seems as if the gremlins actually exist in the universe of the strip, even if the parents deny their existence.
 * One Far Side cartoon involves a man being forcibly lifted by his shirt collar off the ground; the person lifting him is invisible both to him and to the reader. An angry-looking little kid explains, "Big Bob is tired of you saying he doesn't exist."
 * In Richard Thompson's Cul De Sac newspaper strip, Petey has a friend/nemesis Ernesto, an overbearing, insufferably smug fellow - Petey isn't sure if he really exists or not.
 * The Red Dragon in Bone.
 * Then-Flash Wally West eventually learns his imaginary alien friend, Krakkl of Kwyzz, is not only real, but a speedster like himself
 * Stanley's "imaginary" friend, The Monster.
 * The Savage Dragon has an Ascended Fangirl/Stalker With a Crush named She-Dragon, who had seemingly imaginary friends as a result of her initial creation as a parody of John Byrne's fourth-wall-breaking She Hulk. Eventually, however, the voices she was hearing turned out to belong to a group of demigods trapped in another dimension who had a psychic link with her.
 * One Off the Mark strip showed a group of these characters gathered: The Great Gazoo, Pasquale's guardian angel, Hobbes, DW's magical friend, Ida Know, and Not Me, with Hobbes saying "Let's not forget... Snuffleupagus started out just like us and now everybody can see him!". The caption is "Invisible Friend Support Group".

Fan Works

 * In Kira Is Justice, one element of Not So Imaginary Friend is defined and enforced by the author. To prevent Justin from just talking to Landras in his room, where his family might notice, the Telepathy Necklace is introduced. It hadn't been abused yet.

Films -- Live-Action

 * The film Harvey, based on a play.
 * Frank from Donnie Darko. He's literally a six-foot rabbit that no-one besides the title character can see. For good reason, since he's
 * In Heart and Souls, Thomas is a young boy who has several imaginary friends who turn out to be the ghosts of people who were killed in a bus accident. As a grown man, Thomas thinks he's going crazy until he talks to an institutionalized woman who confirms she can see them. She even makes up another ghost to make sure they aren't just humoring each other.
 * In Cooperstown, a retired baseball player is visited by the ghost of his deceased friend. His grandson and his grandson's girlfriend think he's crazy until they confirm (by asking questions about the ghost's batting average) that the ghost really is there.
 * Drop Dead Fred centers on this trope.
 * The title character in Rain Man. As a young child, the protagonist had an imaginary friend known as "Rain Man" who told him stories. Then he grew up.
 * Petes Dragon is heavy on this trope.
 * In Hide and Seek, David doesn't believe his daughter when she said her imaginary friend Charlie killed his wife.
 * King Brian in Darby O Gill and The Little People.
 * Francis the Talking Mule: Everyone could see him, but for the most part, Peter was the only one he would talk to, although it was often subverted when Francis would talk someone else when Peter was really in a jam.

Literature
"Yesterday upon the stair
 * Astrid Lindgren's Karlsson-on-the-Roof behaves as one of these for a long time, although eventually he reveals himself to the rest of the family.
 * Commonly used in the Goosebumps books.
 * Poor Becky from the Shopaholic series spends the first half of the second book desperately trying to convince her family and friend that she is, indeed, dating a famous multi-millionaire. Hilarity Ensues.
 * In Robert Asprin's Myth Adventures series, one volume had a running joke about there being no such thing as Gremlins. Naturally, one did show up at the end of the story.
 * This is the central plot point of Cornell Woolrich's Phantom Lady.
 * Small Gods had St. Ungulant, a hermit who lived out in the desert with the eponymous small gods. His lifestyle involved daily hallucinations, but fortunately his invisible friend Angus was there to keep him from going crazy. Angus later proved himself to be real by braining a hungry lion.
 * The short story "Thus I Refute Beelzy" by John Collier.
 * Making this trope Older Than Radio, the Oscar Wilde story, "The Canterville Ghost". While the rest of the newly-arrived Otis family dismiss the ghost, Virginia befriends him, and ultimately aids in his redemption.
 * Chocky, in the John Wyndham novel of the same name, was thought to be the imaginary friend of a young boy. It turned out
 * In The Graveyard Book, Scarlett's parents think that Bod, the protagonist, is her imaginary friend.
 * In the 44 Scotland Street series by Alexander McCall Smith, Child Prodigy Bertie's therapist believes Bertie's best friend Tofu is imaginary. He's so convinced of this that he makes absolutely no effort to ascertain this beyond asking "Does your mother see Tofu?" (She doesn't, because Bertie knows she never notices anything) and "Is Tofu here now?" (He isn't. Obviously). He then proceeds to make an entire diagnosis based on this assumption.
 * Anna of ''The Woman in the Wall" got stuck in a school employee's handbag because of this trope.
 * In the Arthurian novel Guinevere, a retelling of the legend covering the youth of the future Queen of Camelot, a friend of Guinevere's is considered half-mad because he is acquainted with a choir of very good but invisible singers that only he can hear. Guinevere discovers he's telling the truth because she's able to not only hear them, but see them; however, they agree to keep this a secret between themselves.
 * Arguably the focus of the poem "Antagonish" by Hughes Mearns:

I met a man who wasn't there.

He wasn't there again today

Oh how I wish he'd go away!"


 * In "Mr. Lupescu", a short story by Anthony Boucher, this is done as part of a scheme to Murder the Hypotenuse. Alan wants Marjorie, but she is already married to the wealthy Robert. So Alan pretends to be her son Bobby's fairy godfather "Mr. Lupescu" using an elaborate costume and gains his trust with stories of travels in the Milky Way. He also instills a fear of an imaginary monster called Gorgo that will punish Bobby if he misbehaves. All so that the boy will allow him into the house to meet Robert, whom he promptly kills. "Mr. Lupescu" warns Bobby to tell people what happened or else Gorgo will take him. Of course, no one believes stories of a fairy godfather killing Robert, leaving the police baffled. Alan goes home and destroys his costume, satisfied in the knowledge that Marjorie, now a rich widow, is available.

Live-Action TV
... it sounds as though McBeevee is an Imaginary Friend, and Andy and Barney are skeptical about his existence. Things turn serious when Opie shows his father a quarter (that McBeevee had given him as a present), leading Andy to conclude that his son may have stolen it, and things become worse for Opie when they go to McBeevee's worksite, only to find nobody there. (Shortly before Andy and Opie arrived, McBeevee was called to assist another worker.) Andy decides he has to punish his son for lying, but can't bring himself to do it when Opie insists that McBeevee is real. Just as Andy goes to a clearing to cool off, he muses aloud, "Mr. McBeevee" – and it isn't long before McBeevee responds. "Shatner: Oh, that guy, I've been complaining about him for years, nobody does anything about it. Here, have a copy of my autobiography."
 * Sesame Street: The long-running gag involving Big Bird and his friend, Mr. Snuffalupagus (a large, furry, mammoth-type creature). From his first appearance in 1971 through the fall of 1985, Big Bird would always try to expose Snuffy to his adult friends, but for some reason or another Snuffy would leave and the adults would tease him about his "imaginary friend." Big Bird would then appeal to the audience, "Well, you saw him, didn't you?"
 * The recurring gag was dropped in 1985 and the adults made to see him, some say in the aftermath of the growing awaress of child sexual abuse cases and a desire to catch pedophiles who were thriving because children were keeping silent. It was thought that, with possible victims watching Sesame Street and seeing that Big Bird wasn't being believed about Snuffy, the child might decide to keep quiet.
 * The Andy Griffith Show: "Mr. McBeevee," the 1962 episode where Opie meets a telephone lineman. Because of the way 8-year-old Opie describes McBeevee:
 * He "blows smoke from his ears" (McBeevee, a smoker, is able to make smoke come from his ears when exhaling)
 * He "lives in the trees" (McBeevee's work is often high atop telephone poles.
 * He "has 12 extra hands" (his tool belt and wide variety of tools, which he needs at his side to make various repairs).
 * Topper: Ghosts George, Marion and Neil are only visable to Cosmo Topper, who often double talks his way out of situations of people overhearing him talking to them.
 * Frasier: Frasier not being able to prove he's dating a marine biologist/supermodel.
 * Wings: Joe not being able to prove one of his high school friends is stalking him.
 * Fawlty Towers: Basil not being able to prove a guest has snuck a lady friend into his room.
 * Battlestar Galactica Reimagined: Baltar can see (and feel) Six, which can sometimes lead to some rather frightening scenes. And sometimes hilarious ones. And for bonus points, the "real" Six has a Baltar running around that only she can see. And
 * "Catalina's best friend Suzee isn't there" from Nickelodeon's Space Cases. Saturnian Catalina has an invisible best friend in another dimension that only she can talk to, named Suzee; naturally no-one believes her. This is subverted when an explosion causes the two to trade dimensions and Suzee joins the crew while Catalina is only seen once more through a trans-dimensional viewscreen.
 * The Twilight Zone, "Nightmare at 20,000 Feet". William Shatner's character can't convince anyone, "There's something on the wing!"
 * Spoofed here at 1:43.
 * Also spoofed on The Simpsons when Bart notices a Gremlin tearing apart the school bus. His reward for saving everyone's life? An eternity in a mental ward.
 * Similarly spoofed on Muppets Tonight, where Miss Piggy finds herself on a plane with Shatner.

"Rose: Oh, here's trouble. What you been up to?
 * In The Facts of Life, everyone thought Natalie was making up her biker boyfriend, "Snake". The show went so far as to end an episode with the sound of a motorcycle revving up, and Natalie exclaiming "SNAKE!" (with a quick fourth-wall break to inform the audience they'd have to wait a bit to actually see him). We do finally see him a few episodes later, mostly to set up the Very Special Episode where Natalie is the first of the girls to lose her virginity.
 * We can actually thank Lisa Whelchel for Snake's introduction. The storyline about Natalie losing her virginity was actually originally written to center around Blair. However, Whelchel refused to appear in the episode altogether because at the time, she was (and still is) a born-again Christian and premarital sex conflicted with her morals.
 * In an episode of Monk, no-one believes that Randy's girlfriend Crystal is real. Randy appears to have taken her name from a box marked "crystal glassware," and the picture he has of her is a wallet insert (He explains that she is a photography model). He spends the entire episode trying to convince everyone she is real, even getting her on the phone at one point, to no avail. She is revealed to be real at the end of the episode, driving away in a taxi so no-one can see her.
 * In Monty Python's Flying Circus, the notorious East End gangster Dinsdale Piranha thinks he is being watched by an enormous hedgehog named Spiny Norman. He's right.
 * The Janitor in Scrubs was initially designed as such a character, with the show's creator even intending to reveal him as a figment of J.D.'s imagination if the show didn't last out its first season. In the second season it ended when Neil Flynn asked to be able to work with the other actors. On a DVD commentary he describes his character in the first season as "a Snuffleupagus".
 * In Northern Exposure, Joel initially struggled to convince people that he had been abducted by the mountain man Adam, who everyone else regarded as an urban legend. Adam would eventually interact with other townsfolk, becoming a recurring character.
 * In the long-running Canadian children's show The Polka Dot Door, there was a character called the "Polkaroo" who was portrayed by one of the show's two adult hosts. In each episode, the host in question would find some pretext for leaving the set, the "Polkaroo" would come on and make his appearance, leave, and said host would come back: "You mean I missed him * again* ?"
 * Gilligans Island: In "Gilligan vs. Gilligan", a Russian spy arrives on the island and turns out to be Gilligan's exact double. He starts creating trouble on the island for which Gilligan is naturally blamed, but although Gilligan learns of his presence early on, he can't convince the others of the doppelganger.
 * In The Fugitive, Lieutenant Gerard regarded the One-Armed Man as a figment of Richard Kimble's imagination, conjured up to relieve his guilt over murdering his wife. For much of the first season (until the end of the episode "Search in a Windy City"), even Kimble himself isn't entirely sure that the One-Armed Man really exists.
 * In Unhappily Ever After there is Mr. Floppy the stuffed rabbit, who only Jack the father can communicate with, largely because he is partially insane.
 * One episode of I Carly inverts this, when Sam mentions she has a twin sister coming to visit. Freddie, of course, doesn't believe her, mostly because Sam had pranked him so many time, even when Carly and her brother vouched for Sam's story. But Freddie doggedly refuses to believe it, which is a shame as Sam's sister likes him too.
 * In the short-lived '80s sitcom Jennifer Slept Here, the title character (an old movie actress who had been run over by an ice cream truck) was a ghost who haunted her former house, but was only visible to one member of the family that now occupied the place: a teenage boy named Joey. Much of the show's humor derived from Joey's unsuccessful attempts to convince the rest of the family of Jennifer's existence.
 * The Beverly Hillbillies: Granny runs across a kangaroo which has escaped from the neighbor's place. Everyone thinks she's drunk when she talks about the "giant jackrabbit."
 * In the first season of Home and Away, 8-year-old Sally had an imaginary friend called Milco. 20 years later, she meets her long-lost twin brother, Miles Copeland.
 * The 1960s TV series The Ghost and Mrs. Muir was a sitcom, very loosely based on a 1940s dramatic film. In the sitcom, a young widow and her two children (a boy and a girl) live with their housekeeper in a seaside cottage haunted by the ghost of its earlier inhabitant, a sea captain. The captain chooses to be visible to the widow and her young son, but not to the widow's daughter or the housekeeper, both of whom assume that the ghost is merely the boy's imaginary friend.
 * Doctor Who: After the Doctor meets and befriends the young Amelia Pond, everyone else thinks that her stories of him are just them telling them about her imaginary friend.
 * This gets repeated in the final episode, thanks to some odd circumstances, leading to, and the page quote.
 * Lampshaded with the BBC America intro, which reminds viewers every week that when Amy "was a little girl, [she] had an imaginary friend, and when [she] grew up, he came back..."
 * The Tenth Doctor apparently becomes this to young Reinette in "The Girl in the Fireplace" after popping out of her fireplace, saving her from a clockwork robot, and disappearing again when she was a little girl.

The Doctor: Oh, this and that. Became the imaginary friend of a future French aristocrat, picked a fight with a clockwork man..."

"Jerry: "You sure have a lot of friends; how come I never meet any of these people?"
 * Farscape has Scorpius's neural clone stuck inside John's head. John, being a Genre Savvy guy, named him Harvey.
 * Seinfeld: Kramer has many friends who never appear on-screen (Bob Sacamano and Lomez to name a few). One episode gave us this delightful exchange:

Kramer: "They wonder why they never meet you.""


 * Al Calavicci in Quantum Leap. He's a hologram adviser that generally only Sam Beckett can see and hear (although Al is also visible to animals, small children, the mentally handicapped and the dying). Ninety percent of the time, though, anyone seeing and hearing Sam talking to Al assumes that he's talking to himself, because as far as they can tell, no-one is there.
 * In the Charmed episode "Imaginary Fiends", a demon appears to Wyatt and acts like his friend, all the while trying to corrupt Wyatt into serving the cause of evil. Because only Wyatt can see the demon, the adult characters think that Wyatt merely has an "imaginary friend." The demon, who has done this with other preschool-aged witches in the past, is counting on the fact that adults tend not to suspect that there's anything more unusual going on than just a kid playing with an imaginary friend.
 * A similar plot occurred in an episode of Medium when one of Alison's daughters babysat for a boy that everyone thought was troubled. He would act out, then claim that it was because his imaginary friend told him to. When it turns out the girl can see the "friend" as well, he turns out to be the ghost of a teenager whose girlfriend had left him due to advice from the child's mother. Being a control-freak, after his death he decided to get the boy to act out and drive a wedge between him and his mother as a form of Disproportionate Retribution.
 * Star Trek the Next Generation: An alien takes the form of a little girl's imaginary friend.
 * Lost in Space: The first season episode, "My Friend, Mr. Nobody", has Penny befriending a disembodied voice, that everyone assumes is just her new imaginary friend.
 * A variation on The Invisible Man: the little girl already has an imaginary friend, and Darien uses his power of invisibility to impersonate "Ralph" and get a witness statement from her.
 * On Lost, Ben has an invisible friend named Jacob who can only be perceived by being completely delusional, being innately connected to the island, or by . Jacob is.
 * The Monster of the Week in the Supernatural episode "Playthings" is a spirit posing as the imaginary friend of her grandniece.
 * One episode of Sir Arthur Conan Doyles the Lost World sees Marguerite stepping into a booby trap and falling into a pit with spikes. She gets hurt and while Challenger gets help she hallucinates about her best friend Adrienne who keeps her awake so Marguerite doesn't fall asleep with a concussion. Later it turns out that she's not so hallucinated at all - which freaks Marguerite out.

Music

 * "Bigfoot!" by the Weakerthans is about a man who is exposed to ridicule after seeing Bigfoot.

Puppet Shows

 * For many years (until 1985), Mr. Snuffleupagus on Sesame Street was such a character, seen only by Big Bird.
 * Word of God: In an interview on a documentary called Sesame Street Unpaved, hosted by Sonia Manzano (Maria), Snuffy's performer, Martin P. Robinson, revealed that Snuffy was finally introduced to the main human cast because of a string of high profile and sometimes graphic stories of pedophilia and sexual abuse of children on such news programs as 60 Minutes and 20/20. The writers felt that by having the adults refuse to believe Big Bird despite the fact that he was telling the truth, they were scaring children into thinking that their parents would not believe them if they had been sexually abused and that they'd just be better off remaining silent. Loretta Long corroborated this by uttering the words "Bronx daycare" during Robinson's explanation, a reference to reports of sexual abuse at the PRACA Day Care Center in New York City's Bronx borough, as covered by area TV stations WCBS and WNBC.
 * Around the mid 1970s, children began to see Snuffy. Later on, Muppet characters saw him; Elmo was crucial to helping Big Bird expose the truth.
 * Many children hated how Big Bird was being driven crazy, accused of just imagining him.
 * In fact, future cast member Alison Bartlett O'Reilly would frequently yell at her TV set whenever she saw the scenes.
 * Fraggle Rock frequently has Doc's dog Sprocket trying (and failing) to bring the Fraggles' existence to his master's attention.
 * In one episode, Red discovers the last of the Lily Creatures, but can't get others to believe her. The one Fraggle who does wants to capture and exploit it, so Red "admits" to making the whole thing up to protect it.

Theater

 * Harvey is one of the best known examples of this trope, featuring the charming but batty Elwood P. Dowd, about to be committed for his belief in his best friend Harvey, an invisible six-foot-tall white rabbit. (Changed to seven feet for the film, because of Jimmy Stewart's own height.)
 * Six feet, three and a quarter inches, now let's stick to the facts.

Video Games

 * The Zoni from Ratchet and Clank Future: Tools of Destruction are a group of mysterious little flying creatures that only Clank can see. Naturally Ratchet doubts their existence for most of the game...
 * In Wing Commander II, every now and then you're assigned a solo mission. Invariably, you run up against the Kilrathi's stealth fighters on these missions, and when you return to base you discover that your flight recorder has malfunctioned. Add in the fact that your character claimed to see stealth fighters ten years prior when your carrier from the first game was destroyed -- a claim that was never verified and is still in fact ridiculed -- and it's not terribly hard to see why nobody believes you.
 * One sidequest in Neverwinter Nights 2: Mask of the Betrayer requires you to convince a young magically-talented girl to leave home and train to use her gift. She insists on saying goodbye to what is strongly implied to be an imaginary friend before leaving if you succeed.
 * Spoofed in the game-within-a-game Wing-O in System Shock II. In one solo mission, you meet a new class of enemy fighter, but no-one believes you because you left the lens cap on your flight recorder.
 * That also(?) happened with the Tri-Lackey fighters in the game-in-a-game in System Shock.
 * In Super Mario RPG, Gaz absolutely cannot convince his mother that his Geno doll came to life and walked out the door. She thinks he's lying to avoid punishment for something, though she doesn't know what. Then in walk the heroes with Geno in tow...
 * And then she assumes its a person in a costume. Cue Face Fault from the heroes.
 * In Psychonauts, the childlike, possibly-insane Reluctant Mad Scientist Sheegor claims that if Raz helps her rescue her beloved pet turtle, Mr. Pokeylope, he'll be able to come up with a plan to defeat Mad Scientist Dr. Loboto. And indeed, once you rescue him, Mr. Pokeylope can talk. Like a '70's soul singer, in fact.
 * Koishi Komeiji's presence is ignored by adults, so she sometimes serves as one of these to children.

Web Comics

 * David Hopkins directly references the movie Harvey in "The Case of the Traveling Corpse", a recent story arc of Jack. The comic's titular invisible green anthro rabbit is the "corpse", following a detective who has seen and met him several times throughout Jack's tenure as reaper/Wrath. Of course, nobody believes the detective
 * In The Order of the Stick, Squishy Wizard Vaarsuvius has finally decided to acknowledge the existence of his raven familiar, Blackwing. The rest of the party has chosen not to believe him, despite Haley being the one to remind V about the raven in the first place and giving him his name. Either they are suffering from a severe case of Selective Obliviousness, or they are taking an elaborate form of revenge on him for his earlier failings, in an inversion of Crying Wolf.
 * Maybe they all just Failed a Spot Check?
 * Fluffmodeous from Something Positive. Possibly.
 * Count Your Sheep has Ship, who can only be seen by a young girl named Katie... and her mother, her father, her grandparents, her aunt, her cousin and small animals too. However, Katie never knew her father, her cousin is still a baby and her grandparents refuse to acknowledge Ship's existence unless he angers them. This reduces to three the number of humans he can speak with.
 * in Gallows Humor, the female lead Alma is the only normal human so far who can see the Greek gods. it's a pretty big secret to keep when Thanatos, the god of death, decides he likes your place...

Western Animation
"Sylvester: Listen, I don't blame you if you don't believe me...
 * Batman the Animated Series features a disturbing episode entitled "See No Evil", which features a criminal who uses an invisibility suit to sneak into his estranged wife's house and convince his own daughter that he is her imaginary friend.
 * Aqua Teen Hunger Force: In "PDA", no one believes Shake about Romulox, who turns out to be real. He returns in "The Last One".
 * On Animaniacs, the "Chicken Boo" skits center on someone trying to get others to believe that Boo is a chicken, a fact which isn't made clear until some circumstance causes Chicken Boo to lose his flimsy but surprisingly effective disguise.
 * Hi Hi Puffy AmiYumi does this in the No Dialogue Episode "Ikkakuju", where Ami tries to convince Yumi and Kaz that she really did see a unicorn, but they aren't inclined to believe Ami because she earlier tried to make up a wild story to cover her breaking Yumi's new guitar by accident.
 * On The Gary Coleman Show, Angelica routinely dismissed the demon Hornswoggle as a figment of Andy's imagination.
 * The Evil Monkey in Chris's closet is a running gag on Family Guy. This culminates in season eight, when Chris gets tired of nobody believing him so he actually catches the monkey and proves he wasn't making it up.
 * In a single-episode version, Lois discovers she has a long-lost brother who's somewhat unhinged and talks to an invisible girlfriend. Stewie and Brian decide to place a cucumber where she's supposed to be sitting and declare, laughing, that "if it pickles then she's real". A few scenes later, an angry Lois is heard asking about the pickle on the couch.
 * "The Great Gazoo" in The Flintstones.
 * The Simpsons played with this in one episode, where everyone believes that Homer's new roofer friend Ray (voiced by Ray Romano) is imaginary, but simply missed seeing him due to a series of increasingly improbable circumstances.
 * The event in the hardware shop is probably one of the most plausible, but then Stephen Hawking throws it way out to left field.
 * In one episode of the animated Teen Titans, Raven is stuck with babysitting a set of kids. One of them appears to have uncontrolled telekinesis throughout the episode, and she blames all of it on "Bobby", her invisible super-powered stuffed animal. Raven disbelieves this ridiculous story... until the end, when Bobby the eight-foot-tall super-strong teddy bear drops his invisibility and starts to beat some serious ass on the villain trying to kidnap the kids.
 * Of course Bobby is a manifestation of said kid's telekinetic powers: the girl in question acknowledges this, but insists this doesn't make him any less real. It's hard to argue with her, really.
 * Invader Zim: The title alien is green, with no ears nor a nose, has a cybernetic backpack and says thing like "filthy humans". Yet, only Dib notices that he's an alien after seeing him for the first time. Other people are too dense to realise that a whale floating in midair, ejecting an escape pod, from which Zim and his robot GIR come out... is not normal!
 * Looney Tunes
 * Hymie, Daffy Duck's kangaroo friend from the Looney Tunes short Daffy Duck Slept Here (and an obvious spoof of the original Harvey).
 * Sylvester was repeatedly beaten up by a kangaroo (or "giant mouse", as he mistakenly regarded it) which only he would see. When he tried to show it to someone else (usually his son), they would see an actual mouse instead. Though this was subverted at least twice (with the same dialog to boot):

Sylvester Jr.: But I do believe you, father! There he is right behind you!"


 * Used again in another cartoon where two dogs, a bulldog named Spike and a smaller dog named Chester, decide to beat up a cat to enjoy themselves. They encounter Sylvester and chase him into a junkyard, where a vicious black panther that escaped from a zoo just happens to be hiding out. Every time Spike goes into the junkyard to thrash Sylvester, he is clawed into pieces by the panther, which he, in a dark maze of crates, thinks is Sylvester. Chester has no problem pummeling Sylvester before Spike's eyes, which convinces Spike that Chester must be tougher than him.
 * Used yet again another episode involving the same characters in "Dr. Jerkyll's Hide", where once again the dogs chase after Sylvester. Away from Chester's presence, Spike ends up getting beaten up again by Sylvester, thanks to a potion that transforms him into a giant monster. Chester, of course, never sees this transformed Sylvester, thinking his buddy is being beaten by the tiny tomcat. The final loss of face for Alfie (the name of the bulldog in this episode) is his being thrashed by a fly that has also been affected by the potion, as it occurs in front of Chester's eyes.
 * The same plot was used with Sylvester and Tweety bird, with Tweety thinking a bottle of "Hyde Formula" would naturally be a great place to hide from the cat. He repeatedly turns into a monster, but only Sylvester ever sees it happen, and when the other cats see him flee from the tiny Tweety they think he's nuts.
 * A more well-known short, One Froggy Evening, features a man finding the top-hatted Michigan J. Frog, who would only sing and dance in front of him. Every time he tried to show someone else, he acted like an ordinary frog or just as they arrived he was done singing.
 * Tiny Toon Adventures has its own take on One Froggy Evening. Since singing and dancing animals are the norm there, however, they took it one level further: the frog was (supposed to be) dead. Hamton was about to dissect the frog when it started singing and dancing. Naturally, it only sang and danced when Hamton was the only person looking at it.
 * On Phineas and Ferb, Candace is never able to convince her mother of her brothers' various projects being real because all evidence is destroyed by the end of each cartoon.
 * A running gag is that the entire extended family except their mother is already aware of at least some of it.
 * Timmy Turner has FAIRY GODPARENTS!!!
 * In Mr. Hanky's first appearance on South Park. He was a talking, singing, and dancing piece of poo from Kyle's perspective. But Kyle's friends, parents, and teachers only saw an ordinary piece of poo (along with poo smears everywhere). Kyle's friends have him committed to a mental hospital because they think he's hallucinating. Later, Chef asks them where Kyle is, and the boys tell him Kyle started seeing a magical talking piece of poo, to which Chef responds "You mean Mr. Hanky?"
 * Mr. Hat's just a puppet to everyone (except Mr. Garrison), yet he can drive a vehicle, find his own way into Brett Favre's sauna, and join the KKK w/o any help from Garrison.
 * Happens in an episode of The Powerpuff Girls, where a new kid has an imaginary friend, but others don't notice. So when his imaginary friend starts to play bad pranks, he got blamed until that thing fully plays pranks even without him near, forcing the girls to create their own imaginary friend when they found out that they can't beat him physically.
 * Beth from Total Drama Island has an imaginary boyfriend that no-one believed existed. He shows up at the finale of Total Drama Action in both the original and alternate ending.
 * Spoofed in Harvey Birdman Attorney At Law, where Harvey's client of the week, Ernie Devlin (a Hanna Barbera cartoon character inspired by daredevil Evel Knievel) tries to convince Harvey that a tapir is trying to assassinate him and presents him a photo of an actual real-life tapir. Said gun-toting tapir appears later at the end of the episode to point out a critical flaw in Harvey's legal defense.
 * Back at the Barnyard: A direct animated spin off of the Nickelodeon movie, Barnyard. One of the human characters, Mrs. Beady, repeatedly tries to convince her husband and anyone around her that the titular animals can walk and talk. But everyone just thinks she's crazy.
 * Spongebob SquarePants has the episode of "Bubble Buddy", where SpongeBob's friend, an apparently inanimate bubble, is dragged around for the whole episode. At the very end, he suddenly becomes alive, grabs a Bubble Taxi, and wishes Spongebob a Happy Leif Erikson Day.
 * The Penguins of Madagascar, "Skorca!": Private is on night watch when he sees a giant orca flying through the city streets. The other penguins dismiss it as a hallucination brought on by too much candy, until they actually see it. (It's actually a balloon float.)
 * Ed, Edd n Eddy 's Ed had an imaginary friend named Jib. No one believed he existed until he beat up Eddy.
 * The Season 1 Story Arc of Rollbots is about Spin trying to convince everyone, especially Pounder, that not only Vertex is the crime leader of Flip City (though Penny eventually softens to that idea), but that he is a spiderbot (which nobody believes until Vett appears).

Real Life

 * No one believed then-President Jimmy Carter when he claimed that he was attacked by a giant swimming rabbit while on a fishing trip until a White House photographer came forward with a picture of the event. It was a regular-sized swamp rabbit, quite a bit bigger and uglier than the cute little pet-shop bunnies people think of when they hear "rabbit". Even Carter had to agree it was damn funny; he first presented it as an amusing anecdote from his trip.
 * According to The Jargon File, a "dancing frog" is any bug that occurs unpredictably and cannot be readily induced. Such bugs are extremely difficult to deal with. Again a reference to the cartoon (but predating the trope-wiki).
 * Researchers in 1798 who received a stuffed platypus specimen thought it was a ridiculous hoax, complete with crudely sewn-on leather flap on the bill. But, now, of course, we see the living animal. The same, flabbergasted disbelief happened in reaction to stuffed specimens of the kiwi and the King of Saxony bird of paradise.