In Higurashi: When They Cry, two of the most insane characters actually come the closest to breaking the truth about what actually happened. Rena deduces that the the men in the white van are after her and want to kill her. She also decrees that the men going to see Chie-sensei and tending to their garden was really suspicious. Actually, this turns out to be true, as they are indeed out to kill the gang. The Yamainu drive around in their van and monitor their victims to take advantage of them.
Next, in Tatarigoroshi-hen, Keiichi takes a ride with Takano and notices Tomitake's bike in the back of the car she is in, he questions her and she says it indeed belongs to him. He asks her where he is, but she turns creepy and he wisely gets away from her. He had every right to be suspicious of her. She is the Big Bad.
The one who got the closest was Shion Sonozaki to solving the mystery behind Oyashiro-sama's curse. She correctly deduced that Tomitake was killed by a drug to make him crazy and scratch out his throat, that Rika was coming to inject her with a drug, that someone was following Rena and Satoshi, Hanyuu was following them, that someone wanted the bodies of Miyo Takano and Tomitake to be found, and that Takano probably faked her death. She also assumed that when she thinks of the killer, she thinks of nurses and doctors. Takano was a nurse. If she hadn't assumed the Sonozakis were behind it, she would have stopped Takano.
In Pandora Hearts, the hyper, Lottie says to Jack after he has taken over Oz's body to scare them away, "You're so full of yourself because people call you a hero and somesuch! You must have been so glad when Glen died." Later on, it turns out she was entirely right to suspect Jack. Woo-hoo for Lottie.
In Ponyo, Toki, one of the residents of the nursing home, says to Sosuke that when human-faced fish come out of the ocean, it causes a tsunami. Sosuke sees this as senile rambling— but of course, she's entirely right.
Out of all the characters in Azumanga Daioh, Osaka is the only one who appears to be aware that Kaorin has a thing for Sakaki. At one point, she's also discovered to be a genius at word puzzles.
During Digimon Adventure 02, Miyako pretty much flips out over feeling nervous and starts yelling and jumping around. Her assumed reason for Ken's base disappearing is that it flew away. No one really listens to her because she is so hyped up, but it actually turns out that's exactly what it did.
At some point in the third arc of Durarara!!, Walker and Erika casually decide that Simon and Dennis, the owners and staff of the local Russian Sushi restaurant that they regularly eat at, are secretly Former Regime Personnel on the run from The Mafiya. The next volume proves them completely right.
In Paranoia Agent, that crazy guy chalking random things on the ground? The only one who truly gets what the hell really happened.
In ∀ Gundam, Corrin Nander is quite crazy and violent besides. But he's also the only person to recognize just how dangerous the Gundam really is, having apparently survived a Gundam attack long before the series.
A common event in Katteni Kaizo. For all the times the crap that comes out of Kaizo's mouth has been true, you'd think the other club members would stop looking at him like a brain damaged idiot. Of course...
In Bakuman。 the highly eccentric Nizuma is nevertheless often right about manga. When looking over works that Mashiro and Takagi, Fukuda, and Aoki and Nakai plan to submit to the Golden Future Cup, he predicts that two of them are tied for first place, but refuses to say which to avoid upsetting the one in third. He's correct, as Detective Trap and Kiyoshi Knight- Muto Ashirogi and Fukuda's work, respectively are tied for first place in an unprecedented result.
Free from Soul Eater may be a rather silly and strange person, but he does make a good point about Lord Death acting as an absolute moral authority when it comes to deciding who's good and who's evil, which may work for your Jack the Rippers and your Medusas, but less so when it comes to some of the other witches or Mifune.
In episode 3 of Haiyore! Nyarko-san, Nyarko wonders if Mahiro's Tsundere attitude and skill with forks mark him as a descendant of the cursed deity hunter from the "forbidden black book". In episode 4 Mahiro's mother returns home and everyone learns that she's a (part-time) deity hunter who's also deadly with forks.
It actually happens semi-regularly in this series, most often with Nyarko trying to identify the Chekhov's Gun that will turn out to be the lynchpin of the current crisis. Mahiro almost always dismisses her suggestions because they would make for a really stupid resolution...and he gets really ticked off when she's right. There was even one incident where Nyarko dismissed her own suggestion as being way too contrived, so naturally she was 100% correct.
In Yu-Gi-Oh! GX there was Princess Rose, a Society of Light member in the second season. She certainly seemed to be rather spacy (even more so in the dub, where she talked like a Valley Girl). A fan of the fairy tale The Frog Prince all her life, she insisted that she could see the Spirits of the Des Frogs in her cards, much like Judai and Manjyome could, giving them names and calling them "princes". However, Judai wasn't able to see them (although he tried to keep open minded) and Manjyome was downright rude to her about it, calling her insane (You might be able to chalk a lot of that up to the fact he was brainwashed at the time). However, after Judai finally won the duel, he finally was able to see one of the Spirits she was speaking of; it seemed they did exist, though the spirit was a humanoid frog in a suit rather than a handsome prince like Rose thought.
The pro-demilitarization faction in Sidonia seems pretty silly on its face: they believe that the only reason the Gauna are attacking is because of humanity's constant aggression, and they believe the Kabizashi (the only weapons capable of permanently killing Gauna) draws the Gauna to Sidonia. They're half right- the Gauna are attracted to the Kabizashi, but abandoning those weapons did nothing to prevent the Gauna from attacking their demilitarized colony ship.
I Luv Halloween - In the midst of a Zombie Apocalypse (which none of the cast care about as long as they get their Halloween candy), Finch's psychotic little sister believes that the "Chonklit monkeys" live in everyone's bowels and are responsible for replacing the Halloween candy with their poop. This later proves to be true, as a pair of monkeys pop out of a zombie's stomach and discuss their plans for another poop takeover.
In Watchmen, Rorschach and The Comedian both play this role to an extent.
The Sandman: Delirium of the Endless is one serious cuckoolander with bipolar tendencies. Nevertheless the members of the Endless family tend to embody not only what there names might suggest (dying, despairing, destroying) but also the opposite (being born, hoping, re-/creating). Delirium claims more than once to know things that even Destiny - the guy who has everything about the universe written down in his big book of all that was and will be - does not. Is she just boasting? Or is she - due to the Endless' duality - the queen of the cuckoos and secret keeper of true enlightenment combined?
Destiny seems unconcerned about everything except the immediate future; While he knows what does happen next, Delirium might know everything that could happen.
Delirium is capable of becoming sane at will, but it causes her great pain to do so. This might suggest that the other half of her dual nature is in fact the sort of merciless, soul-crushing reality that makes people go crazy in the first place.
From the same series comes Mad Hettie, a minor-league witch whose primary power seems to be wrapped up in her immortality. She's perpetually homeless and crazy as a bedbug to boot. But when she gives you a warning... especially if you're just some guy walking down the street... you'd better freaking listen, because your whole life might depend on it.
Deadpool is convinced that he's a fictional character in a comic book, but since he's insane other characters dismiss this along with his other delusional ramblings.
In Oh God Not Again, Luna is the only person to figure out Harry and Sirius time-traveled. It seemed obvious to her. Harry himself who comes off like this to others, as most things he says are bat-shit insane yet are almost always accurate not matter how over the top they are (he knows what's going to happen because he's from the future).
In Anthropology, the human-obsessed Lyra goes to to absurd lengths to try to prove that humans exist. She hasn't yet proven it in her world, yet.
In All You Need Is Love Naomi Misora's paranoid conjectures turn out to be accurate more often than not.
Mega Man Recut has this. In "The Strange Island Of Dr Wily", Dust Man makes a ridiculous rant about the Bermuda Triangle and how the island Wily is going to is haunted. Considering all the weird stuff that starts happening shortly after Wily and the Robot Masters arrive, he had a pretty good point.
Back to the Future: Doc Brown's eccentric nature forces everyone but Marty to believe he's a crackpot (and in some ways - see the "mind-reading helmet" from 1955 - he really is), but he did invent the time machine...
In The Happening, the plants really were the culprit, just as the somewhat eccentric character claims in the beginning.
Really, most of his cuckoolander elements were there to test Luke. While he's not without a sense of humor, he's pretty serious during Luke's training.
When Dory from Finding Nemo attempts to communicate with a whale in his own language, she appears to just make a fool of herself. Turns out he caught every word and gives her and Marlin a lift to Sydney. Which eventually leads to this priceless moment with Marlin wishes to express his gratitude to the whale:
Marlin: THAAAANKKK YOOOUUUUU SIRRRRRRR! Dory: [Impressed] Wow. Wish I could speak whale.
Walter, the resident PTSD stricken (or so he likes to believe) Vietnam veteran in The Big Le Bowski formulates a theory that Bunny kidnapped herself, and that the toe with green nail polish sent to her husband by German nihilists is just an empty scare tactic. While the latter is never revealed to anyone other than the audience, it still turns out that Walter, though crazy enough to pull a gun on a man over a game of bowling, sometimes knows what he's talking about. Or it was a lucky accident.
In Land of the Lost, Will suspects the alien is lying to them based on his policy of "never trust anyone wearing a tunic". The others dismiss his concerns, but later we find out that not only was he an imprisoned criminal but part of his punishment was to wear a tunic as a symbol of his distrust.
Grandpa Simpson in The Simpsons Movie—"Twisted tail...a thousand eyes...trapped forever... EEEPA! EEEPA!"
Lampshaded later on: "My god, the crazy old man in church was right!" By himself.
In Scanners II: The New Order, when Peter Drak informs David Kellum of Commander Forrester's bad intentions, David dismisses it with "You're crazy!". Drak points out that while that may be true, it doesn't mean that he's wrong.
In R.E.D., Marvin Boggs (John Malkovich's character) is more then a little paranoid. Over the course of the movie, he thinks a helicopter if following them, that the CIA is tracing a phone call made on a pay phone, and that a woman at the airport is actually an assassin who is following them. None of the other characters believe him, but as it turns out, he's 100% correct, every time.
In the horror film Mother's Day, the eponymous character is the matriarch of a sadistic band of psychopaths, who is terrified of an imaginary monster named "Queenie". Little is made of this, until the main characters appear to have escaped danger...
The guard at the French castle counts as well. At first it seems like he has no idea what the Holy Grail even is, yet his claim that "we've already got one" turns out to be the truth.
Sir Bedevere is full of strange wisdom, such that the earth is banana-shaped or that sheep's bladders may be employed to prevent earthquakes, and in his introductory scene determines that a woman is a witch if she weighs the same as a duck. However, when tested on the scales, she does, and mutters "'Twas a fair cop". She really was a witch after all.
Not necessarily: when she and the duck are removed from the scales, they're seen (in the background) to be uneven.
Reporter: Los Angeles, New York, and Washington D.C. have been left in ruins.
Russel Casse: Good God! I've been sayin' it. I've been sayin' it for ten damn years. Ain't I been sayin' it, Miguel? Yeah, I've been sayin' it.
In Dark City, everyone believes Detective Eddie Walenski has been driven mad by the stress of his job, the horror of the serial killer case he'd been working on, and other pressures. Walenski, on the other hand, keeps saying that there is no case, his wife is not his wife, that things keep changing on a nightly basis, that everyone's past has been erased, and the only way out of the trap they're all in is to kill oneself. He is, of course, utterly and completely correct.
In the film Conspiracy Theory, Mel Gibson's character prints a newsletter called "Conspiracy Theory", filled with conspiracy theories about anything and everything under the sun. Everyone, possibly even including himself, thinks he's just another crackpot with an axe to grind. Then the assassins start chasing him.
In Ghostbusters 2, Venkman interviews 'fake' psychics on a little-watched cable show - but one of his two guests actually turns out to be a real psychic, and correctly predicts the events surrounding Vigo and his plans for the world.
YMMV on whether he was psychic or just lucky; his prediction only almost came true.
Rosemarys Baby: This happens to Rosemary. It turns out her neighbors were indeed part of a satanic cult that, with the help of her own husband, impregnated her with the son of Satan during a creepy ritual and were forcing her to stay on a disgusting diet to ensure that her hellspawn would be born strong and healthy.
In Rear Window, Jeff, who spends entire days peeping at his neighbors, tries to convince everyone around him that one of the neighbors killed their wife and hid the body. And he's 100% right.
Mose Harper in The Searchers is looked on by everyone as a crazy old coot and is actually shown to be wrong on a couple of occasions at the beginning of the movie (about Ethan Edwards having gone to California and about the cattle-rustlers), but later on, on two occasions, he supplies crucial information about the whereabouts of Chief Scar and his camp.
In Godzilla (2014), Joe Brody’s obsession with his wife's death has left him more than a little nutty, but he was still right about the cover up.
In Cat People, Oliver and Alice belatedly realize this about Irena's stories about the cat curse.
She's a Ravenclaw for a reason, and her answers to the Ravenclaw Tower's questions in Deathly Hallows were pretty smart. She takes after her father Xenophilius, who is just as strange, but 100% correct about The Deathly Hallows.
Some of the stories from The Quibbler have a grain of truth to them. For example, Sirius may not be Stubby Boardman, but it does get right that he was an innocent man falsely imprisoned.
For the first four books, Hagrid's status as the Fluffy Tamer and Admiring the Abomination, usually the Monster of the Week is regarded with bemusement and dread by Ron, Harry and Hermione, but even Hermione, highly friendly and compassionate, has a nervous breakdown when he returns to Hogwarts with his Giant Half-brother who he's trying to teach English, not caring that it could possibly endanger every student at Hogwarts!!! Everyone expects this to be Hagrid's greatest folly but it turns out that...Hagrid's crude attempts at teaching his brother English and civilizing him worked!!
Also from Harry Potter, Sybill Trelawney is an amiable lunatic who everyone thinks is a complete fraud... until she issues two True Prophecies that affect the plot of the entire series. She actually predicts a lot of minor stuff, but she seems so much of a fraud that nobody seems to take her words for any merit; probably because she has the habit of hopelessly misinterpreting the actual omens she sees. It's heavily implied that she has the gift, passed down from previous generations, but just can't control it, making her most genuine prophecies in a trance-like state that she doesn't remember afterward.
Remember when she kept mentioning that big black dog that appeared as an omen to Harry? She (and some others) interpreted it as a Grim, but then the dog's true identity came out...
In book 3 Trelawney predicts that Harry will DIE. ...And she is absolutely right - she's just four books early. Moreover, every prediction she makes in the opening fusillade of her first class does, eventually, come true in some capacity.
It can't help that one of the few times she's right even she doesn't believe it: in HBP when she's reading cards and draws the Knave of Spades "a dark young man, possibly troubled, one who dislikes the questioner" just as she's standing next to Harry's hiding spot, only to decide that couldn't possibly be right. She might actually have some talent aside from the two Voldemort related prophecies she doesn't remember but is simply unable to differentiate it from her desperate guessing since she wants it so much.
Another one she gets right is the tarot card of the "Lightning Struck Tower"- a card which figuratively means great calamity and/or change. And then there's the chapter by the tarot card's name, where a green bolt of "lightning" hits Dumbledore at the top of a tower and kills him. Yeah, that certainly changed things, and not for the better.
Also, Ron Weasley's prediction in her class - that Harry will suffer but will be happy about it - sounds very much like what happens in the end, too.
A meta example. Tara Gilespie, author of the notoriously bad fanfic My Immortal correctly guessed the final plot twist ( In her words "nd den hairy wil have 2 kommit suicide so voldimort will die koz he will rilly be a horcrox!!!!!". The only real innacuracies are the Voldemort did not die immediately, but merely became vulnerable, and that Harry got better.) in great detail.
In the new Foundation trilogy novel Foundation In Chaos, one of the characters references a lunatic fringe group which committed suicide when told by creatures inhabiting the defense platforms of the impending end of Trantor. When you read the earlier novel, you find the creatures indeed said this and they were right — the Galatic Empire is collapsing and Trantor lies in ruins in later Foundation novels.
Played with in The Hitchhiker's Guide to the Galaxy: Ford Prefect appears to be a Cloudcuckoolander to the humans he interacts with - he spends a considerable amount of his life drunk, he tends to insult astrophysicists when he is, and he often lapses into distracted moods wherein he stares at the sky and claims he is looking for green flying saucers. However, when he flippantly informs everyone at a local bar that the world is about to end, he's absolutely right. Somewhat averted in that Ford Prefect is not what he seems - he's simply an alien trapped on Earth and desperate for a ride off the planet, so he has advanced technology and actually knows more about what's going on than anybody else around him.
In A Fire Upon the Deep by Vernor Vinge, there's a galaxy-spanning Usenet-like network where various aliens discuss the book's crisis, from a number of different perspectives. One particular alien, "Twirlip of the Mists", is talking through several layers of auto-translation software on an extremely low-bandwidth connection, so most of what it says sounds rather bizarre. It's pretty much all exactly right, though, including such apparent nonsense as "hexapodia is the key insight".
Despite often engendering befuddlement and bewilderment in many he comes into contact with, Psmith almost never lets anything ruffle him, since almost any obstacle that comes his way he can eventually overcome. Even his most outlandish schemes seem to end as he intended.
Zeghorz from Will of the Empress seems crazy to start with, but it turns out that he actually hears and sees things on the wind, making all of his babbling completely true.
Donny DaCosta from Troubleshooters might be crazy and spot aliens all over the neighborhood, but when one of them turns out to be a terrorist...
The prisoner Numbers from Airman only babbles apparently incoherent numbers, which are crucial for the plot development.
In Catching Fire, it turns out that Wiress's mumbling of "Tick tock" isn't just insane talk. She's actually figured out the configuration and theme of the arena and is trying to tell the other contestants. Katniss figures this out later on. "Tick tock, tick tock, the arena's a clock."
In The Faerie Wars Chronicles, Alan Fogarty is a crazy old man who believes that faeries inhabit his garden, that Little Green Men in flying saucers are kidnapping people all the time, and that the FBI is after him. The hero of the story humors him... until he discovers a fairy in Fogarty's garden. Later, it's revealed that demons from a Hell Dimension (who look oddly similar to the zeitgeist little green man) do in fact kidnap people regularly from their stereotypical flying saucer airships. Also that he used to be a bank robber, so his paranoia about the FBI is at least somewhat justified.
When Shin-tsu tells you he played cards with Santa, you better believe him.
Robbie, William Marsh's loony younger brother, gives Lewis vital clues as to what the hell is happening in London. However, it takes some time for Lewis to realise, since Robbie has wrapped what happened to him into a deranged fantasy.
Robbie: 'They sounded like angels speaking in my head. They spoke about the tide. Oceans singing black songs and requiems for fallen God and empires. The dark tide shall rise, rise through the houses of the dead.'
G. K. Chesterton loved this trope, employing it in such works as Manalive and Napoleon of Notting Hill
Heck, Chesterton himself sometimes comes across as this due to his rather unique way of expressing himself.
A Song of Ice and Fire: Lysa Tully is crazy ten times over, but her warning to Catelyn about the Lannisters' treachery doesn't seem to be far off, only she lied. The murder of her husband, which was what supposedly tipped her off to the Lannisters, was perpetrated by her.
In Janet Evanovich's "Seven Up", bounty hunter heroine Stephanie Plum is initially skeptical toward Mooner's worries about his friend Dougie (and a roast from the freezer) disappearing, and later doubts his claim that his assailant was an elderly lady, since Mooner is notorious as a Cloudcuckoolander and a stoner, who's lately taken to running around costumed as a superhero. Of course, it turns out he was actually telling the truth.
In The True Meaning of Smekday, Gratuity's mother Lucy insists that aliens are trying to talk to her through a mole in her neck. She disappears shortly before the Alien Invasion by the Boov. Later on, Gratuity finds out that the Boov were talking to her through the mole on her neck, and abducted her to teach them English.
The Orks as a race in The Sovereign Stone Trilogy. They're massively into reading omens before making any remotely significant decision, causing most members of other races to dismiss them as superstitious Cloudcuckoolanders. That said, Ork characters accurately predict events in the trilogy using aforesaid omens with a striking degree of accuracy, and in the third book, when the protagonists try to fool the Ork leader with a fake omen into helping them, she sees through it immediately, and is in fact mildly offended that they seem to think she "can't tell the difference between an omen sent by the gods and an omen sent by an elf."note she still helps them, though, because the Orks have a stake in this conflict too
The Sherlock Holmes parody "The Case of the Mental Detective" in "Soft Pawn", a chess fun book by William R. Hartston. All clues in the case of the hated chess master (not related to Bobby Fischer) killed by eleven knives in the back point to...eh, a typewriter thrown from a giraffe unicycle by an Irish sailor with a cold called Keffeagh Q. Bacdabb?!? ("Bacdabb?" "Actually Mac Nabb, but he's got a cold.") But, being Sherlock Holmes, he's of course right. ("You got me, it's only fair I turn myself in.", as Bacdabb confesses.)
The Log Lady from Twin Peaks issued dire warnings that turned out to be completely accurate.
River from Firefly, although in her case, she's messed up because she was kidnapped by the government and tortured in order to refine her latent psychic powers. A specific and very clear example:
River: They weren't cows inside. They were waiting to be, but they forgot. Now they see sky, and they remember what they are.
Mal: Is it bad that what she said made perfect sense to me?
The entire gang from The Office struggle to remember the security guard's name, only certain that it begins with the letter E. "Edgar?" "Elliot"? "Edward"? Resident Cuckoolander Creed interjects that his name is Hank, and Creed, of course, is correct.
Spencer from Burn Notice. He's schizophrenic and sees messages encoded in beams of light, but he's also smart enough to see the pattern between the actions of his boss and the deaths of American spies. On the other hand, the conclusion he draws from this is that his boss is a space alien...
The Hybrids in Battlestar Galactica. They're prophets, but most of them, most of the time, are so cryptic and vague that except for one instance no one has any idea what they mean (the phrase "harbinger of death" kind of stands out). But in hindsight, everything they said was accurate or at least relevant.
Bridge in Power Rangers S.P.D. is weird, but usually on the ball. There's his initial warnings about A-Squad in the beginning; or his complete avoidance of Dru in "Idol", which were brushed off at the time. Guess which characters had a Face-Heel Turn later. Plus his dreams in "Idol" and "Robotpalooza;" considered nuts and irrelevant at the time, later proven thematically relevant and literally accurate, respectively.
When Bridge reappeared in Power Rangers Operation Overdrive, he explained how he became the Red Ranger since we last saw him. As weird as it sounds, viewers who watched SPD will know it's entirely accurate:
Bridge: Well, long story short, our mentor, who's uh, well, who's a dog, got promoted to head of SPD which used to be run by a bird, but he retired and went down to Miami and then Sky got promoted and then I got promoted, and that's why I'm the Red Ranger! Or rather, will be.
Spike remained Dangerously Genre Savvy even when he went crazy after getting his soul back and getting Mind Screwed by the Big Bad of season 7, so much so that, in the episode "Same Time, Same Place", he's the only one to figure out that Willow can't see or interact with the rest of the Scoobies and vice-versa. Of course that was only because he was interacting with them at the same time, and noticed they couldn't see or interact with each other.
Drusilla babbles insanely, thinks she can see the stars right through her ceiling, and worries about her dolly Miss Edith. All of her ramblings turn out to be psychic predictions, meaning she's a Mad Oracle.
In Earshot, Xander falls between this and Dumbass Has a Point when he jokes that the person Buffy telepathically overheard planning mass murder was probably the lunch lady and her terrible cafeteria food. He eventually discovers he's right while sneaking into the kitchen to steal jello.
Nobody ever listens to poor Zathras, although they probably should've.
G'Kar definitely had his cuckoolander moments... and almost everyone ignored his warnings about the return of certain eldritch abominations until it was nearly too late. The ones who didn't ignore him were already planning for it and feigned ignorance while letting his world burn to maintain the ruse.
A Taxi episode shows Jim to have an ability to predict things. Alex, rational thinker that he is, dismisses it, but Louie, who considers Jim a total bum, believes that's his one talent, and warns Alex to heed an ominous premonition where he'll be mistaken for a woman and will dance the can-can in a green sweater.
Dalek Caan flies unprotected into the Time Vortex to bring back Davros. He emerges from this experience completely insane, but with the gift of prophesy. The Supreme Dalek prefers to ignore his ravings, but Davros knows he speaks the truth. Sure enough, he predicts that one of the Doctor's companions will soon die, and Donna essentially does because the Doctor must wipe her mind. It also turns out that some of the episode's events happened because Caan was manipulating them to destroy the Daleks. An alternate interpretation is that rather than Donna (who though she loses her memory doesn't actually die), the one Caan was refering to was Davros himself. As the Dalek mothership explodes around them, the Doctor ushers all of his companions into the TARDIS to escape, including extending an invitation to Davros, offering to save him. Davros refuses, and stays to go down with the ship, and it is at this moment that Caan laughs maniacally and repeats the prophecy that "one will still die". The Doctor's invitation to Davros could be seen as promoting Davros to companion, albeit briefly, and thus Davros' death fulfils the prophecy.
Lampshaded by River Song:
Octavian:[about The Doctor] You trust this man?
River Song:I absolutely trust him.
Octavian: He's not some kind of madman, then?
River Song:[beat] I absolutely trust him.
This is almost a Running Gag on The X-Files. No matter what crazy theory Mulder comes up with to explain aspects of a case or what logical theory Scully comes up with, Mulder is often right.
An episode of the The Big Bang Theory has Sheldon crazily demand that Penny get rid of a chair she found on the street and paid a homeless man to carry up the stairs because he's convinced it must be filthy. He gets Amy to talk to her, but she confesses to Penny that even she thinks he's paranoid. Then they realize there's a rat in the chair.
In Til Death, there's a version with some Unfortunate Implications where white guy Eddie sticks up for his Black Best Friend Kenny when he claims he's been racially discriminated against, but Eddie is soon convinced Kenny is just overreacting when he hears the other side and the remainder of the episode is about him trying to convince his friend he's oversensitive. In the tag, however, it's revealed that it was racism after all.
An early episode of LOST involves Claire freaking out because she thinks someone's trying to abduct her and hurt her unborn baby. She's had a bunch of weird nightmares she's convinced are true, despite not being plausible even by Lost standards, and Jack thinks this is just another delusion. Turns out, there are other people on the island and one has been abducting her for medical tests.
Zora from Sonny With A Chance reacts to Dakota by turning around, widening her eyes and hissing in as demonic a voice she can muster. "Eeevilll". She turns out to be right.
The title character of Merlin, constantly. A bit of a subversion in that he's not really a Cloudcuckoolander, but since nearly everyone else believes he is, this happens nearly Once an Episode. Arthur eventually catches on to this and starts consulting Merlin on everything.
Occasionally, a contestant on QI will quip a completely bizarre answer to a question for laughs... only to be awarded points. They're usually just as surprised by this. Examples include when Jack Dee blurted out that the original geishas were all men, and when Johnny Vegas correctly joked that the purpose of corn flakes was to prevent masturbation.
Carrie Mathison in Homeland is bipolar, although she controls it with medication; this, incidentally, is not played for laughs at all. She is nevertheless the only one who figures out that Brody is working for Abu Nazir, and figures out what Nazir's plot is. It's during a manic phase that she figures out a timeline of Nazir's activities that is the key to deciphering the larger plot.
Abed's vast knowledge of television is generally accurate given that he's in, well, a television show, and every once in a while he falls into this trope. In the third season, while in therapy, he occasionally comments that the dean's been replaced by a "doppeldeaner". Which is a statement that the audience knows full well to be true, although the characters take some convincing.
If it's even possible, there's a kind of inversion in the first season. Shirley adamantly believes that the accuracy of Abed's films mean that he can predict the future. When confronted with this, Abed denies any prophetic abilities, a belief he starts to doubt when his films continue to come true regardless of the absurdity.
In a way, Sarah from House of Anubis. While she isn't really a cuckoolander, many people do believe she is crazy including the main characters themselves, but everything she says is usually a clue to the mystery in some way. This is because she grew up with the mystery herself, as her parents were the ones who hid the treasure and the two main villains turned on her for the truth. She also happened to be the original Chosen One.
Sesame Street has Sherlock Hemlock, who always comes up with zany explanations of the "crime scene" (but was right at least once).
Kamen Rider Double has Shotaro Hidari, half ofthe eponymous hero. Unlike Philip, Double's other half, Shotaro has no superpowers as a normal human. One of his cases required him to find his client's cat. Reasoning that the best way to find somebody is to think like they do, Shotaro decided to wander around pretending to be a cat (meowing, batting at invisible string, etc) until he found the real one. He succeeded.
The music video to "Weird Al" Yankovic's "Foil" has him rant off the typical government/alien conspiracy theories while wearing an aluminum foil hat at a cooking show. The director appears to be annoyed that he's ruining the show... until he calls two guys in black suits and sunglasses to sedate and take Weird Al away. The director then takes off his human face, revealing himself to be a reptilian.
In the Vampire: The Masquerade, the Malkavian clan are like this, as they were all insane in one way or another, but tended to have a hidden insight that was frequently ignored by the more sane clans due to their weirdness.
A perfect example of this is the beggar woman in Sweeney Todd. She has the greatest awareness of the characters' secrets in the musical but people disregard her because she seems crazy. Tragic when you find out why she seems to know so much.
Rosencrantz of Rosencrantz and Guildenstern Are Dead. The general rule is that Guildenstern is the smarter of the two but talks in circles, while Rosencrantz is a bit dim but usually hits the nail on the head (even if he doesn't know it himself).
Their predecessors, Vladimir and Estragon from Waiting for Godot, have a similar dynamic, with Vladimir as the misguided intellectual and Estragon as the understanding fool.
A Very Potter Musical, and this is quite the spoiler: Draco insists that Hogwarts is a terrible school and he's going to get transferred to Pigfarts, which appears to be him making up completely random nonsense for attention: Pigfarts is on Mars, is run by a lion named Rumbleroar, which is suspiciously similar to Dumbledore's name, and of course no one else has ever heard of it. When it's suggested Draco go to Pigfarts and leave the heroes alone, this prompts Draco to flip out and berate Harry for not having a spaceship. But then, near the end of the play, Rumbleroar actually appears to Dumbledore and flies him off to Mars, and in A Very Potter Sequel, it turns out that Luna is familiar with Pigfarts as well.
One of the major premises behind the Deus Ex series, most notably in the first and the third games, is that every paranoid conspiracy theory you've heard is right.
The Nameless Moddiscusses this premise in the fan fiction shop, and has this from a hobo you encounter in Forum City, who mentions that he saw aliens abduct Deus Diablo.
Shegor in Psychonauts says her turtle, Mr. Pokeylope, "always tells me what to do." Right when you assume she's projecting on the poor little thing, the turtle starts talking. In a deep, sexy voice, it outlines a plan you must follow to advance further in the game.
Rosa the Thin-Blood will frequently descend into long and nonsensical speeches about such things as "The Crimson Ship" or "The Voice In The Darkness, Boss." And, of course, as the game slowly progresses, Rosa's prophesies start to come true. It is implied that she is a Malkavian Thin-Blood. Because she is a Thin-Blood, she manages to stave off madness much of the time and remain mostly sane. Because she is a Malkavian, during the times when she does descend into madness what she says usually means more than it might seem at first glance.
A Malkavian protagonist will have quite a few moments like this, too, often casually dropping atomic-bomb scale foreshadowing and revelations into dialog. It looks like a Malkavian PC is just a Talkative Loon, but almost everything he says has a hidden or double meaning. Emphasis on almost, granted...
In both cases, however, neither of the characters actually understand what they are talking about: They merely see glimpses of things without the necessary context to comprehend it. An example is when the Malkavian encounters Ming Xiao and refers to her as "The Mistress of Mirrors", which angers her. She is a shapeshifter (thus 'reflecting' others), but the Malkavian doesn't know that.
One of The Deb of Night's regular listeners is Gomez, a loony Conspiracy Theorist that rambles utter nonsense about traffic lights with cameras monitored by The Illuminati and the like. However, in his final call to the show, he not only mentions the secret vampire society but goes on to pretty much summarize the entire plot of the game.
Star Control: Virtually everything the Pkunk say sounds like lunatic ramblings. Ignore them when they tell you where they got their information ... but don't ignore the information itself.
It doesn't help that they sound like Miss Cleo without the accent.
Early in Bioware's Mass Effect 1 we get Manuel, a quack on Eden Prime that raves incomprehensibly about an end of the world scenario and is treated as insane by his companion. WAY later on in the game the team learns that his doomsday rants are more accurate than you originally thought. The accuracy of his rambling has lead some fans to theorise that Manuel might have also glimpsed the Prothean beacon's message and his mind was destroyed, as Liara suggested might happen to someone who, unlike Shepard, lacked the extraordinary willpower to handle it.
A Dr. Manuel Cayce appears in the second game during the Firewalker missions, where Shepard investigates a series of planets in the Hammerhead. These planets detail a Dr. Manuel's search for evidence of Reaper invasion including text documents showing his growing paranoia over whether his associate had become indoctrinated (Dr. Manuel decides to make sure and kills him) and leads the player to a huge floating Prothean sphere artifact that shrinks down to the size of a bowling ball when touched. Shephard then uses it as a centerpiece. While never stated outright if he is the same doctor in game (though apparently confirmation at one point in development did exist, it's the same voice actor portraying him and he mentions not letting another Eden Prime take place.
One Volus billionaire claimed that he had a vision of "machine devils" and went to great experience trying to excavate a world where he believed tombs of a special race capable of defeating them were buried. While the second part never panned out, his claims were noted as being not so outlandish in the third game.
Roadkill in Twisted Metal 2 where he was called crazy for believing that the whole thing was All Just a Dream but in the end of the story Calypso believed him, granted his wish, and he woke up. Or did he?
The old bag-lady you meet near the beginning of Alan Wake seems to be just another crazy old tramp, ranting about the importance of changing light-bulbs and whatnot... but considering the nature of the game, it should come as no surprise that she knows EXACTLY what's going on, and EXACTLY how to fight it. In fact, she's the ONLY one who knows, due to being excluded from a bout of reality-alteration that made everybody else in the world forget. With her true title as 'The Lady of The Light' revealed, she ends up playing a huge role in the last half of the game. She's still a tad crazy, though.
Fallout: New Vegas gives us No-Bark Noonan. After taking too many radscorpion stings to the head, he's taken to coming up with bizarre theories. There's also a sidequest to help a religion of ghouls make it to the moon. Afterwards, No-Bark can be heard on the radio claiming that the strange occurrence near the religion's HQ was "Religious ghouls, with rockets, lookin' for a land to call their own."
No-Bark is not exactly right on a couple other accounts, but still give pertinent information: He describes a monster (invisible shimmer, mad ranting, minigun - ie, a Nightkin) that had been slaughtering the livestock, but thinks it's a Chupacabra. He also spies the Legion slavers entering the hotel reception room to talk with Jeannie May Crawford on the night that Boone's wife was kidnapped, but thinks it's mole people. Both cases he's dead wrong, but both cases lead you to solve the associated problem.
How "wrong" he is involves how deeply you look into the meaning of what he says. For example, the Chupacabra is believed to feed by sucking the blood of animals and killing them, and it's name is translates roughly as "goat sucker." It's not a far stretch to look at the general description of the quest, which is that during the night some of the livestock are killed by a means that leaves lots of small holes in them by something nobody has been able to see. While it isn't exactly what No-Bark thinks, it does nearly fit the cryptid to the T. If you also look up the meaning of mole in context, you'd see that it's fairly accurate as well - her behavior does suit the definition, although she is more of a slaver than a spy.
Benny seemed to take Noonan seriously as well. The one attribute everyone seems to remember about Benny on the road is that he has a cold, impersonal look in his eyes in spite of his attempts to appear affable by using 50s lingo and wearing a nice suit. Noonan, who thought his suit was to disguise himself from aliens, tells Benny that his camouflage does work, but that he needs the same camouflage on his face.
He's actually a slight subversion. Initially, he doesn't initially believe ghouls are involved with that quest. He claims it is commie ghosts that want to paint Lenin's face on the moon. He doesn't start claiming that it was religious ghouls until after the quest. Presumably, he could have heard it from the Courier at that point.
Rena of Shira Oka: Second Chances does seem to be a bit of a loon with her constant talks about spirits and ghosts but she really does have these powers and that her magic potions really work.
Steins;Gate uses this as its primary plot element. Protagonist and self-proclaimed Mad Scientist Kyouma Hououin (birth name: Okabe Rintarou) sees conspiracy in everything, blaming even minor, everyday inconveniences on the shadowy machinations of the world-spanning Organization, but since he's pretty much harmless, those around him just let it slide. So when he starts raving that SERN has been researching Time Travel with the ultimate goal of enslaving humanity, and that his microwave is the only thing that can stop them...
In Jables's Adventure, Squiddy mentions meeting the Princess. Jables replies that he didn't know there was a princess in this game. Squiddy admits that neither did he. Nevertheless, after you defeat the final boss, the princess shows up out of nowhere for you to rescue.
In Portal 2, a certain broken turret you can save from "redemption" known as the oracle turret spouts some rather cryptic lines like "Don't make lemonade!" and "Her name is Caroline". All of it foreshadows events in the latter half of the game.
In several The Elder Scrolls games, the book Chance's Folly tells the story of a thief by the moniker of Chance who brings a 'crazy' Breton named Ulstyr Moresby along on a treasure run, and learns that his seemingly insane "Yes, yes, yes, prop a rock, hot steel. Chitin. Walls beyond doors. Fifty-three. Two months and back." actually referred to breaking into the tomb, avoiding traps, wearing the proper kind of armor, one-way locking stone doors, the number of gold bags within, and waiting two months for poor Chance to die off in order to return and take the gold himself.
In Hatoful Boyfriend, Anghel Higure is a bird who's... not quite right in the head. Just for starters, he's convinced that he's a Fallen Angel and the heroine is his reincarnated love Edel Blau, regularly crashes through glass windows and loudly proclaims that he can sense demon spores that must be eradicated at once, and treats even the most pedestrian decisions as life-and-death matters. However, in the Bad Boys Love route, it turns out that at least one part of his ramblings actually has validity to it: the "demon spores" he keeps on ranting about and senses the most strongly in the infirmary were most likely the Charon virus Doctor Shuu was preparing to infect Ryouta with in the same infirmary, which indicates that he can actually sense diseases/viruses that no one else can.
There's a scene where Anghel can talk to Nageki Fujishiro, who is baffled. Partly because Anghel is... being Anghel, but also because he's talking about things from before Nageki's death five years ago that he should have no way of knowing.
It goes far beyond this, in fact: After you've completed Bad Boy's Love, going back to the regular routes and listening to Anghel again will leave you with the mind-blasting realization that everything he says, which once came off as complete nonsense, describes the events of that plot perfectly, leaving you with the impression that perhaps Anghel is the only sane bird at St. Pigeonation's.
In Alpha Protocol, many of the conspiracy theories that Steven Heck rambles on about actually happened in Real Life (Operation Acoustic Kitty), could be argued to have actually happened (his theory about the collusion between the Federal Reserve and private banks to screw over the American people), or can be revealed to have actually happened in the game (his theory about the government screwing with commodity prices in order to manipulate people's minds; if you ask Mina to dig up intel on Parker, she will send you an email noting that that was the subject of his doctoral dissertation).
The sequel to Nelson Tethers: Puzzle Agent introduces a woman called Korka who lives in the town and also suspects something strange is going on. However, after she reveals that she suspects that everything is about a bigfoot that lives in the area, Nelson promptly leaves and calls her crazy in his audiolog. Guess what creature ends up helping him destroy the lunacy ray?
At the beginning of Alpha Prime, the utterly drunk Freddie (and later, the eccentric Paolo) keeps insisting that this prospector's urban legend "Glomar" is a real creature who is the source of hubbardium. While not quite literal, by the end, it's undeniable that Glomar is definitely some kind of real, extraterrestrial force that creates hubbardium out of the rocks surrounding its heart, among other things.
Agent Francis York Morgan from Deadly Premonition. Some of the things he says to his imaginary friend Zach who is really the player as well as some of the things he envisions when staring into his coffee are often foreshadowing of future events Oracle-style. Likewise, his unorthodox procedures often yield hidden evidence, contrary to the expectations of those around him. A lot of his words and actions are dismissed by the sheriff in particular, at least early on. Of course, while York is definitely odd, he is arguably normal in-verse considering how strange most of the residents of Greenvale are.
Yahtzee Takes On the World: World leaders consult a magic eight-ball to make decisions. When a main character asks a ball about Yahtzee's odd behavior, it answers "He's the Anti-Yahtzee, dumbass."
In Megatokyo, Largo is treated as a Cloudcuckoolander by most of the class, but Tokyo IS a World of Weirdness, and personal relationships DO lead to more trouble than would be expected. Early on, he was telling Piro and Erika about his encounter with a horde of zombies, and nobody took him seriously, including most of the audience, who recognize that Largo is way too obsessed with video games, and when he says he was being chased by zombies, it was probably just a crowd of goths or fanboys he had managed to upset. Years later (or a week in webcomic time), the zombies return, and it's explicitly shown that they're flesh-eating monsters from another dimension. Piro and Erika still don't believe him.
Done in Schlock Mercenary, by Lieutenant "Pi" Pibald (who is "every bit as irrational as his namesake"), who correctly guessed the true nature of Credomar.
Later he correctly identified why a rampaging Gav-clone turned super soldier was killing all his victims with head injuries; If Balt Binion came back with a different personality after his head was regenerated, it's likely that all the transmogrified Gavs will come back with a similarly hostile personality.
Schlock also throws around really wild guesses, some of which hit precisely.
Something like this happens in Sluggy Freelance during the Boys' Night Out arc. Early on, a vampire hunter is introduced, and even though one of the oldest recurring characters really is a vampire, this hunter is initially portrayed as being humorously and/or dangerously out of touch with reality, to the point that you might expect him to kill innocent people, and the fact that vampires do exist seems to be a mere coincidence. Fast-forward to the end of the arc, where this crazy hunter has been overpowered and kidnapped by legitimately evil vampires, and he reveals himself to be a Crazy-Prepared unkillable badass.
In one chapter of The Adventures of Dr. McNinja, two guys are in a graveyard at night, roleplaying Dungeons & Dragons. By sheer coincidence, zombies burst out of the ground at the exact moment one of them casts a spell to raise the dead. Incredulous, he cries out "Jack Chick was right!" as they flee.
In Gunnerkrigg Court Jack stops eating in an attempt to avoid Court staff, on the belief that they track people through their food. Jones later confirms that this is how they usually do it.
In Blip, K becomes concerned over a flash of light outside the airplane window, fearing that it's from an alien spacecraft. Two pages later, we see that the plane nearly did collide with a UFO.
In Drowtales, no one believes Kiel'ndia when she suggests that her friend Naal'suul might not have been completely taken over after releasing her demonic seed and that she might still retain some of her old personality but a few chapters later it's proven that she was exactly right. She's also the only character in the story who actually realizes she's in a comic, which everyone else dismisses as more crazy talk.
In Vinigortonio Jose constantly speculates that things that obviously exist are illusions much to Vinicius and Igor's annoyance. And he turns out to be right about the bomb in the third comic.
In 8-Bit Theater, the utterly idiotic and insane King Steve is devastating the environment by ordering his subjects to drill the earth for mana despite such a thing being impossible. In the penultimate strip, a newspaper reports the discovery of a "mana vein".
One chapter of Broken Saints features eccentric egg farmer Masayuki, who tells a silly story to Kamimura (one of our heroes), and is hardly seen again. As it turns out, the moral of that story is the central message of the whole series.
In one of the endings to the Atop the Fourth WallSilent Hill: Dying Inside review, Linkara is transported into the Cloudcuckooland that is Phantasmagoria. When he speaks to Pollo, Pollo responds with "His soul is blue. His heart is steel." It's a reference to Mechakara and a clue to his identity — specifically, that he's actually an alternate universe Pollo.
In We Are Our Avatars, Kari points out that, technically, it was Arcie's fault for letting the other Legendaries in the Pokemon world grow up to be so dysfunctional, Arcie agrees.
In Red vs. Blue, a lot of the seemingly crazy things Caboose says actually turn out to be right (at least to some degree) in the long run. For example, in the first season he thought that Church was "a gay robot", and six years later comes the big Reveal that Church was in fact an A.I. rather than a human. After a time travel episode, he also notes that "Time... line? Time isn't made out of lines. It is made out of circles. That is why clocks are round." which actually fits with the eventual series theme of events going in circles.
In Worm, Glaistig Uaine is a psychotic mass murderer who thinks she's a faerie Queen, and makes a number of bizarre claims that no one takes seriously, though they humor her because she's incredibly dangerous. Pretty much everything she says turns out to be foreshadowing, though it's actually caused by aliens, not faeries.
In G2G: Got to Go, Maggie's new age spiritualist friend Rainbow is most often right when people ignore her ramblings of universal imbalance and the like.
American Dad! - While in the middle of a drug-fuelled Mushroom Samba, Roger refused to let go of a big bag of cat food, afraid that he was becoming immune to gravity. At the end of the episode, he drops the bag and floats off.
Kiina from BIONICLE strongly believed in life on other planets, and wanted to leave her Crapsack WorldDesert Punk planet and visit them. Naturally, everyone thought she was nuts until Mata Nui showed up.
In South Park: The Imaginationland Trilogy, Mel Gibson, over the course of a masochistic rant, suggests to government agents that they look over the individuals in a terrorist video, looking for someone who 'doesn't fit,' which turns out to be the hint they needed. Different from most of these cases because the agents instantly recognize it as such. "Say what you want about Mel Gibson, but the son of a bitch knows story structure!"
In "Reverse Cowgirl" Butters admits he thought the correct way to sit on the toilet was to sit inward so you can rest your reading material on the top and reach the handle without having to look down. Near the end John Harrington's ghost confirms that this is how he intended it to be used.
In Stroker and Hoop, Stroker is hired by a very rich man with a tinfoil hat claiming that Ron Howard was psychicly talking to him. He wanted Stroker to investigate. Stroker accepts the money, and walks off. Then Ron Howard starts contacting Stroker with his psychic powers, which Stroker blocks out with a hot dog wrapper.
On The Simpsons, when Springfield was threatened by a comet, the only one not panicking is Homer. He's convinced it will burn up in the atmosphere and be "no bigger than a Chihuahua's head." At the end of the episode, that's exactly what happens (it even lands next to a Chihuahua for comparison).
Bart: But what's really amazing, is that this is exactly what Dad said would happen.
Lisa: Yeah, Dad was right...
Homer: I know kids, I'm scared too!" (Family hugs, terrified)
Bart, when his ADD medicine caused him to become paranoid. He became convinced that Major League Baseball was using a satellite to spy on the populace, and stole a tank to shoot it down. Mark McGwire, fresh off of his pursuit of the home run record, immediately showed up to distract everybody's attention.
When the family put their valuables in a fire-proof safe, we see Bart's Krusty doll falling on Lisa's Malibu Stacy convertible turning its headlights on lighting Homer's cologne bottle causing it to boil and explode. When they see the safe smoking, Homer guesses exactly everything we've seen, but Lisa denies it as ridiculous.
Marge briefly becomes paranoid in "It's a Mad, Mad, Mad Marge", thinking that Becky is planning to kill her and steal Homer, but every accusation she makes is debunked and everyone thinks she's crazy. At the end, however, when she finally concedes she was wrong and apologizes to Becky, Becky confesses and says she had planning to kill her, at least originally. (According to her, she had a lot of trouble buying a shovel and decided to scrap the whole idea.)
In Alvin and the Chipmunks Meet the Wolfman, Alvin makes various crazy claims about people in the neighborhood being monsters that get him in trouble. He has never been right, which his brothers ridicule him for, and Simon uses them as evidence that his claims their new neighbor is a werewolf are wrong. Then Theodore is bitten and turns into a werewolf, and it's eventually revealed that their new neighbor is the one who bit him.
"Swarm of the Century," only Pinkie Pie recognizes the adorable bug Fluttershy found in the forest as a troublesome (and rapidly multiplying) Parasprite, but her attempts to gather up the needed equipment to get rid of the swarm is seen by her friends as her being her random self. The fact that she says "I need this instrument" without explaining why she needs it, only strengthens this preception and they gripe that she isn't helping them round up and dispose of the bugs. That changes when she managed to lead the swarm out of Ponyville.
Used in "Over a Barrel," where she attempts to settle things between a western town of ponies in Appleoza and a tribe of buffalo. Unfortunately, she does so via a ridiculous song and dance number that irritates the two groups even though her message is the best solution for the both of them.
And in "Feeling Pinkie Keen", she turns out to be right about her "Pinkie Sense", a series of symbols that she claims to allow her to predict the future.
Happens in Invader Zim when Dib tries to escape the school nurse who declares martial law during a lice outbreak and rambles about a giant queen louse being responsible. She's right.
Dib himself is perceived as a Cloudcuckoolander by... everyone except Zim and Gaz. The entire series is about Dib actually being right about Zim being an alien when no one else believes it.
One episode of Kid Notorious starts with an Almost Dead Guy ranting about a Nazi conspiracy to wipe out all the Jews in Hollywood. Everyone else remembers last week, when he thought Bill Cosby wanted to drain his blood, but Evans does some digging, and, well, you can guess.
Dave the skunk from Scaredy Squirrel is this trope at times, especially in the robot hammock episode.
In the CatDog movie, there's a running gag where Dog explains several ridiculous theories detailing how they became separated from their parents, ranging from them being abducted by mole people to getting amnesia and consequentially believing they were country western singers. When they finally find their adoptive parents, these wacky theories turn out to be true.
Legion Of Superheroes has a variant—Brainiac-5 is malfunctioning and as a result, babbling incoherently. During his rants, however, he starts to reveal information about Superman that he himself doesn't know yet. Of course, neither Clark nor Timber Wolf understand what he means.
Crocker's theories in Fairly OddParents are spot on, and he's the only person outside of other kids with fairies to recognize it. He usually manages to correctly predict what Timmy has wished for, even if he went from a completely absurd starting point to reach that conclusion, and some of his anti-fairy gear actually works, somehow.
Dale Gribble once correctly deduced that Chuck Mangione was secretly living inside the Arlen Mega-Lo-Mart. The audience gets to see what led him to believe the pest was a person instead of a rat, but how he figured out that it was Chuck specifically is anyone's guess. It seems like just another one of his ridiculous conspiracy theories for most of the episode, until Chuck reveals himself to Dale.
In "Old Glory", when Bobby is getting low grades, Peggy assumes the teacher is getting revenge on her for taking her coveted parking space at the school. We may think this is Peggy being a Know-Nothing Know-It-All as usual until the end when it turns out to be true.
On Gravity Falls,Mabel is helping Dipper uncover a historical conspiracy to prove that she's not "silly" like Pacifica said. However, throughout their quest she keeps unconsciously doing ridiculous things which help them solve the clues. Ultimately, it's revealed that the person who laid the clues was just as big of a Cloudcuckoolander.
Lt. Maj. Goose: (Beat) Curly! Go stand in that corner facing inward!
The trope is a plot point in one episode of Family Guy where Peter hears from a random guy in a chicken suit that the world is going to end on midnight during New Year's Eve. Naturally, Peter's family refuses to believe him, but after he shoves them into the basement and they survive doomsday, Peter spends the rest of the episode telling everyone he was right about the world ending.
Matt Bluestone of Gargoyles. He's convinced there are gargoyles that patrol the city at night, and that the Illuminati exist, control even the President, and are part of an Ancient Conspiracy that stretches back to the Middle Ages. If this were a more reality-based show, he'd be nuts, but in this show, everything he believes is true. Not only that, but he eventually becomes the gargoyles' Friend on the Force and actually joins the Illuminati.
Botch suspects The Hair Bear Bunch is using a variety show in their cave as a ruse for them to escape (episode "Closed Circuit TV"), but Peevly, watching on his closed circuit monitor, is entertained by the proceedings. Turns out Botch was right—the bears are seen parachuting over the wall for a night on the town.
Happens fairly often in mathematics and science. Quantum mechanics is surely Cloud Cuckoo Land material, and it's been proven correct at every test. Relativity is similar, if a LITTLE easier to understand.
Dr. Michio Kaku famously said "It is often stated that of all the theories proposed in this century, the silliest is quantum theory. In fact, some say that the only thing that quantum theory has going for it is that it is unquestionably correct."
Niels Bohr: "If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet."
Also Niels Bohr: "We are all agreed that [quantum theory] is crazy. What divides us is whether it is crazy enough to have a chance of being correct."
Edgar Allan Poe's 1848 prose poem "Eureka," where, falling into dementia and having professed skepticism about mathematics as a tool of scientific discovery, he uses his own "ratiocination" (read: free association with elements of proto-logic) to decide that the universe had arisen from a singularity, that there were celestial objects so dense that light cannot escape, that many of what were then thought to be nebulae were in fact galaxies as large as the Milky Way itself, that the solar system was at the edge of the Milky Way rather than the center, and that Newtonian gravity was a special case of a broader property of matter. Of course, there are also many, many errors, but it's still pretty impressive for a document that reads like a nineteenth-century Time Cube.
This Cracked article had 5 cases of people who had 'insane' thoeries that was proven to be true.