The students of Class 3 in the Anime/Manga/Light Novel Another manage to force and subvert this trope, in an effort to stop the calamity that kills off members of the class and their family members. Due to the calamity being caused by one person in the class actually being dead, it can be averted if the class ignores one person in the class and pretends they don't exist. They originally choose Mei Misaki, until the protagonist ends up talking to her, having not being briefed by the class on how to behave. This starts the calamity all over again, and the students even resort to ignoring the protagonist himself, with no success.
Also present in that the one dead person in the class is impossible to detect, since everyone in the class and town and even the dead person themselves have no recollection of their death—at least, that is unless you kill them, in which case everything goes back to normal and everyone, except for the person who returned them to death, remembers them for how they really died, and has no recollection of their ever being in the class.
Naruto should be the Master of Selective Obliviousness. For example, he didn't realize Hinata had strong feelings for him, something many of the other ninjas were easily able to figure out.
He also doesn't realize that Sasuke really doesn't want to come back to the village, even after Sasuke impales him and almost kills Sakura and Kakashi.
In Ranma ½, the bombastic Tatewaki "Blue Thunder" Kuno refuses to believe that the hated Ranma Saotome and his beloved "Pigtailed Girl" are one and the same, even when Ranma changes right in his arms. After a while, one wonders if he isn't fully aware and just forcing himself not to think about it. His sister has a similar ailment, but she isn't confronted with the evidence quite as often (and in the anime, never) and actually tried to figure out what happened before getting sidetracked. Kuno might also be purposely ignoring all of the blatant evidence that neither of his "love interests" actually even likes him, let alone lusts after him... although this may be less Selective Obliviousness and more a cocktail of Casanova Wannabe grade lechery (Kuno is debateably a Handsome Lech) and whopping ego.
Akane Tendo is often accused of this regarding the fact that her pet pig is actually the cursed form of one of Ranma's rivals for her affections.
Hell, Akane Tendo practically lives this trope in both canons. It's got to be the biggest problem she brings to the relationship, even worse than her insecurity. That's not to say that Ranma doesn't contribute his own flaws, faults and problems, but when she's been shown to consciously ignore Ranma's attempts to explain how a situation wasn't what it looked like, to the extent that the manga version of Akane ignored Ranma's outright telling her why he was trying to grope Hinako, coupled with showing her the pressure point chart he was using, in order to support her own belief that it's because Ranma is an uncontrollable lecher... well...
To be fair to Akane, some of the situations really do look that bad (naked with Shampoo in the furo in a very suggestive pose for example) and in regards to Hinako, he was practially attacking her several times in her introduction arc, very much coming off like a pervert by grabbing her breasts, and without any explanation, it's doubtful that anyone would believe him.
It's genuinely understandable really. While there are a few times she goes off on Ranma when he really is innocent, the majority of the time he really IS at fault and he and she knows it. Frequently enough that he really doesn't deserve the benefit of the doubt.
In the anime canon, this flaw is actually the explicit reason why Akane is a Lethal Chef; she refuses to follow the recipe and adds extra ingredients that she ''believes'' will make it even better (and then adds the wrong wrong ingredients, due to not looking at what she's grabbing), and refuses to admit her cooking habits are why nobody will ever eat her cooking unless forced. In one episode, she spends the entire night trying to make edible cookies and continues to repeat the same mistakes over and over even though each and every batch turns out terrible. When Ranma finally allows himself to be guilted into eating her latest batch, and promptly takes to his room with severe stomach pains, Akane idly declares that the recipe must have been faulty.
Kasumi Tendo calls people who are actively trying to murder Ranma his "friends". Often Flanderized in Fan Fic into one of her defining traits.
Granted, considering Ranma's training tactics and his talent for annoying people, most of the people who look like they're trying to murder Ranma actually ARE his friends.
Mousse could be called Selectively Oblivious in regards to Shampoo. He refuses to admit that the girl he's been chasing since they were three has never shown any sign of reciprocated interest, at best ignoring him and more commonly hitting him whenever he made one of his "romantic" gestures/speeches. By the late manga, she's perfectly willing to let him die just to be rid of him. Instead, Mousse blames her lack of interest on her (willingly given and clearly backed by genuine emotion, at least in the anime) engagement to Ranma and frequently assaults the Japanese boy, accusing him of seducing Shampoo or otherwise keeping her away from Mousse.
Revolutionary Girl Utena was interesting in that it didn't portray the girl (Shiori) practicing Selective Obliviousness in a positive light.
One can also argue that Utena starts indulging in this after episode 31.
In Cromartie High School, no one (except Kamiyama, Hayashida, and the Doctor that preformed the school physicals) seems to notice that Mechazawa is, in fact, a robot.
The same for the student gorilla.
Kyon of Suzumiya Haruhi very deliberately ignores any hinting that the Chessgame of Life may have a King (who decides the game) as well as a Queen (who has the power in the game); he refuses to acknowledge Tachibana flat out telling him that he has the power to transfer Haruhi's power as well as Tsuruya's telling him that he and his friends really need to work on their Masquerade better.
And then there's just his ignoring Haruhi's feelings for him; over which she's willing to rewrite the whole of reality over. Even Itsuki is starting to get annoyed.
Souichi of the Boy's Love manga The Tyrant Falls in Love doesn't seem to realize that he's making an awful lot of exceptions to his homophobia in regards to his gay companion Morinaga, not even after he says outright that he doesn't want Morinaga to leave him and that he can have sex with Morinaga only. That must be one hell of a balancing act between "I hate hate homos!" and "I can't let Morinaga leave my side, even if he likes me that way!" in Souichi's mind.
Nearly the entire cast of Hayate the Combat Butler has this about one subject or another (Sakuya, for example, believes her destiny is to become Japan's greatest comedienne, with Nagi as her partner).
Ouran High School Host Club: Tamaki persistently interprets his attraction to Haruhi as paternal affection; hilarity, naturally, frequently ensues out of the dissonance. Aside from Haruhi herself, no one else is fooled, and in later volumes the other members of the Host Club speculate that Tamaki subconsciously refuses to acknowledge his feelings for Haruhi because he doesn't want anything to break up the surrogate family he's created in the Host Club the way his parents' love caused his own family to be broken up.
The funny thing is, Tamaki's "paternal love" obsession goes a bit far when he realizes he's romantically in love with Haruhi. He thinks of himself as a "perverted lech" preying upon his "daughter" and feels horrified about committing "incest".
Penguin Revolution: It takes Ayaori six manga volumes of rooming together and, finally, actually seeing Yukari naked (with his contacts in, for a change) before he realizes that Yukari is a girl pretending to be a boy instead of a boy pretending to be a girl. Sure, he's Blind Without 'Em, but Yukari pretty much stops trying to keep the act up around him before the first volume is over.
In Detective Conan Ran has had suspicions about "Conan"'s identity, but not nearly as often as she should have, all things considered. (In one instance, Conan was terribly ill; he reverted to his normal appearance while nobody was watching him thanks to a drink he had been given by Heiji, then solved the mystery. He had a conversation with Ran, while obviously still very sick, then fell down the stairs and vanished in a puff of smoke. She heard Shinichi scream from nearby, and when she investigated, she found Conan instead. And somehow, she didn't figure it out.
Well, one could argue that she is satisfied for a while when there's a proper explanation. And she does try to trick him more than once. It seems that she kind-of accepted it as a fact by now, but she's waiting for Conan to tell her.
What about Heiji? He actually labelled his jealousy, when Kazuha flirted with a magician, as a 'leader's concern' for his follower....!
There was a Fan Fic take on this which suggested that Ran is, in fact, hoping she's wrong because she's Genre Savvy enough to have realized some of the implications of what she had been able to figure out, and would like to avoid going farther.
Satou's very much aware of Takagi's affection for her at least relatively early on, and she definitely reciprocates it. What she isn't aware of is how much nearly every other male detective in her department is crushing on her (well, except for Shiratori, but that was only because she got stuck in an omiai with him), to the point where she never seems really aware why the Absolute Defense Line keeps making things difficult for the hapless Takagi. She doesn't even realize that any ring on her left ring finger will typically symbolize engagement! On the other hand, considering that the last officer she was attracted to died at a mad bomber's hands...er, explosives...she may just be subconsciously tuning out anything that could lead her into that sort of devastation again. Takagi's genuine love for her is the only thing capable of getting through that membrane.
Misa in Death Note is fairly intelligent, and professes to be talented when it comes to romance (and might well be), but refuses to see that her beloved Light actually hates her.
In Axis Powers Hetalia, England doesn't seem to comprehend what colonial America meant by "Go to hell, England". Even in the present, he thinks of how cute of a kid America was.
To be fair, that was a very early strip and it seems to have been retconned since then. All the later strips show the relationship between England and little America as genuinely warm and fluffy, with little America pretending to enjoy England's cooking even though it's horrible, being happy to receive presents from England, and crying when England goes home.
Spain actually has this moreso than England, especially in the strip where he proposes to Romano. He merely asked for three meals a day without the slightest hinting to either option, but Spain automatically takes it as rejection.
America also fits in this, as Word of God states that he "refuses to read the atmopshere". In other words, he can literally choose whether to remain oblivious to an event or finally pay attention to it.
Russia seems to think that other nations actually want to live with him. When one of them rebels and he does have to face the fact that they all hate him except for Belarus, he doesn't seem to have a clue why.
More recently, Denmark has been hinted to do this as well, ignoring aggressive social behaviour and maintaining a cheery demeanour. He never gets it whenever Norway insults him, and during the 2011 Halloween event, when Belarus throws a hanger at him and declares that Russia's team will win, he simply wished her luck.
Then there's Japan's reaction after he and Greece had sex: "IT WAS ALL JUST A DREAM! I'M SO GLAD IT WAS JUST A DREAM!"
Sousuke from Full Metal Panic!. In the beginning, it looked more like he sincerely never notices when characters are in love with him. However, as the series goes on, it starts becoming more and more obvious (as his suitors become more and more direct) that he's actively turning up his obliviousness. This is no doubt due to his atypical upbringing, he probably has no idea HOW to react to such affection. His relationship with Tessa comes to mind, in particular. Numerous times, she makes incredibly aggressive advances on him, which he actually notices enough to feel nervous and scared. However, when people are later referring to her feelings for him, he's shown to react in a very oblivious manner, many times completely dismissing it.
Yurika in Martian Successor Nadesico tends to do this, insisting that Akito is head-over-heels in love with her, even though he's never shown any signs of it and tends to get pretty annoyed when she tries to get close to him. But it's possible that her obliviousness is all part of a master plan to make Akito fall in love with her. if so, it works.
In Monster, Eva manages to overlook the fact that she had mistreated Tenma in the worst way - and when he tells her, nine years after she had broken off their engagement, that he is flattered but uninterested in reconciling, she chooses to turn a deaf ear and threaten him with telling the police that he had killed her father should he really decide to continue his life without her.
In Moyashimon, Aoi Mutou used to work hard at part-time jobs so she and her boyfriend could afford a place together. But one day, she arrived at his apartment only to find he had moved out, taken the money they had saved, and left a note saying he had found someone else. Mutou preferred to believe that he had been abducted by aliens, which is how she fell in with the agricultural university's UFO Club. Any attempts to bring up the obvious truth simply drive her to drink.
CLANNAD: Upon learning that his daughter, Nagisa is pregnant, Akio is torn between denial ("A stork brought it, right?"), joy at becoming a grandfather and wanting to strangle Tomoya for getting her pregnant. He does eventually (grudgingly) accept it. This is a rather extreme case, as Nagisa and Tomoya have been married for several months at that point.
Yamamoto Takeshi is the poster boy for this trope. He has seen talking infants wield guns, come very close to dying at least three times, traveled forward in time to stop an Omnicidal Maniac from destroying the world, and still thinks the mafia is an role playing game Tsuna and Gokudera cooked up. After being specifically told this isn't a game multiple times.
He takes game seriously though, not selective obliviousness in his case... he is just plain oblivious and idiotic. He definitely no longer think this whole mafia business a game once they transported to future, maybe before that he already was depend on your opinion how serious he was in battle. Hard to say since he smiled in 80% of his fights...
Ikuto in Nagasarete Airantou is this to anything supernatural, dismissing it as his imagination or putting it into logical reason, despite living on a daily basis with talking animals and a kappa.
When Ikuto's sister is introduced it's revealed that she is actually a youkai and that he has been cursed to prevent him from realising.
In Skip Beat!, Kyouko is completely oblivious to the fact that Ren is in love with her, even after his assistant blatantly told her.
Though she does have a Freudian Excuse, as after the guy she was in love with pretty much admitted he only saw her as free labor, her feelings of love died.
As a Running Gag in Eyeshield21, Mamori continiously misses the signs that Sena is Eyeshield 21, despite Sena practically Clark Kenting. She knows Sena has the same build as Eyeshield 21, that Sena joined the football club, never saw Eyeshield 21 without his mask and Sena always seems to disappear when Eyeshield 21 shows up. She thinks "Everytime Eyeshield 21 shows up... Sena never seems to be around. Maybe they... don't get along well?" The justification is that since she still sees Sena as a little kid who cannot stand up for himself, she simply cannot think of him as a successful football player. It's even lampshaded by Hiruma: "Preconceptions are harsh..."
Sandra also falls into this trope. She REFUSES to believe that Greg has been raping Jeremy.
It's possible that Angela/Ash is this in Black Butler. She/he commits horrible and very sinful actions and yet, she/he believes that it is for the work of the Lord. See Well-Intentioned Extremist to understand this.
Can be seen in Western depictions of a Superhero with a secret identity, attempting to tell it to the loved one. (Example: Spider-Man's Aunt May.) One Superman story has Lois admonishing the Man of Steel for "that creepy Clark Kent impersonation." (Indeed, one might make a claim that the whole Superman mythos embodies this trope, as it would seem painfully obvious that Superman is just Clark Kent without glasses.)
In the 2000s, Aunt May found out Pete was Spider-Man, and called him out on not telling her, pointing out that she had survived the death of his parents and Uncle Ben. She also said that for a while, she had thought he was gay. Peter burst into laughter.
J. Jonah Jameson generally frowns upon "costumed vigilantes", considering them usurpers of law and order. But he is willing to give the devil his due when it comes to true acts of heroism and is considerably lighter on those he feels have "paid their due" - like Captain America. Of course, there is a big Spider-Man-shaped blind spot in this P.O.V. - which, Depending on the Writer, can range in severity from Running Gag (Robbie Robertson constantly having to talk Jonah down from some of his more libelous headlines and editorials) to outright insanity (the newly-elected mayor of NYC Jameson gleefully watching a S.W.A.T. team open fire on Spidey without provocation.)
Robbie Robertson occasionally hints that he knows perfectly well who Spider-Man is, but that he can't acknowledge it. If he "knew," then he'd be morally and professionally obligated to tell his best friend and boss J. Jonah Jameson.
It's implied that, if Commissioner Gordon wanted to, he could figure out Batman's identity, but he deliberately chooses not to, and has in fact refused to look when Batman offered to reveal who he really was.
In Batman: Year One, he's standing two feet away from Batman who, out of costume, just saved his infant son's life and hands him the child. Gordon blames the loss of his glasses for his inability to recognize the man.
In the Dick Grayson Batman era, it is repeatedly all but stated that Gordon knows who Batman is and more importantly, who he was.
It's painfully obvious that Doctor Doom, being a supergenius and all, should be able to realize that Reed Richards had crap-all to do with the malfunction that caused Doom's experiment to blow up in Doom's face, and was only trying to explain to Doom that the experiment was flawed. However, Doom apparently can't stand the idea of Reed being smarter than him, so he steadfastly refuses to see reason and continues to try to destroy Reed's life in "revenge". It's hinted he does know this full well deep down though, as whenever Reed calls him out on this bullshit, he tends to fly into a homicidal rage, and at least once started beating Reed into a bloody pulp while screaming at him to admit he sabotaged the experiment "or else!"
Also, Loki often claims things like "everyone hated me" which may or may not be true. While most of Asgard does indeed dislike him, Thor himself often references that he and Loki were happy together as children, and Loki just seems to block that time out so his Freudian Excuse is more credible.
Now he does know, since many people of Asgard were nice enough to point it out for him that his scheme led to The Sentrybringing Asgard crashing down. However, they are also unwilling to tell him almost anything else (like who people are, what is happening at the moment, etc), since they still want to off him the second they think Thor won't care. The only exceptions so far seem to be the Warriors Three, who seem to do so very grudgingly (unless the story is funny or makes who Loki used to be look bad).
Kyon's mother in Kyon: Big Damn Hero refuses to acknowledge that Kyon had to get into a fight because of Tsuruya when she is told that Kyon had to replace Tsuruya's bodyguard, and instead decides to be full Shipper on Deck between them. And that was after scolding him for getting info fights at school (which happened because of Tsuruya too).
Light: [Stephen]'s oddly pleasant considering the last time we met, and I swiftly come to the conclusion that L hasn't told him that he loves me and that we're just going through a rough patch which involves impacting my face with his fist.
In Parting Words, Princess Celestia realizes that the Cutie Mark Crusaders have never received adequate help for their bullying problem because the adults are so wrapped up in their own duties and obligations that they convince themselves that the foals' problems are unimportant and not worth their time and effort.
Fluttershy in the Reading Rainbowverse didn't seem able to get that Macintosh wanted to break up with her without hurting her feelings. Even when Macintosh considered the manner settled, she failed to get the memo. Only after coming back from vacation and seeing him with Carapace did she realize what was going on... leading to a drunken rant atop a drunken dragon.
In Cultstuck, most of the titular cultists are unable to see Karkat as anything other than the perfect, infallible reincarnation of the Sufferer, and they interpret the slightest mundane thing he does as divine revelation. Karkat, on the other hand, is severely annoyed by this, as it means that none of them are really acknowledging him as a person or listening to his opinion. (He's tried to stop them being selectively oblivious, but...well, they are a cult.) This is played for laughs, but also drama: they expect/force Karkat to fit their image of the Sufferer, and have spent centuries producing propaganda and warping history to fit their beliefs.
Similarly to the above, Lereal Belsai of Hivefled refuses to believe that Karkat isn't simply testing his faith and genuinely isn't magically able to protect the Child Soldiers of the cult. He also dismisses Gamzee out of hand as a spy, despite obvious marks of torture on him.
Mars Attacks!. Art Land is so intent about selling the investors on building his casino that he ignores the all out alien attack going on outside.
A creepy example in Shutter Island. An asylum inmate subconsciously created an elaborate illusion of residing in her neighborhood, and treated other patients and staff as neighbors or delivery men, flatly refused to admit that she's been committed for murdering her children. Then the unfolding story reveals that the protagonist suffers from that very delusion and that he created a far more elaborate illusion that placed him in the shoes of a federal marshall investigating the escape of the aforementioned inmate from the asylum and secretly searching for another inmate that killed his wife. In fact, the nonexistent escaped inmate is his wife, that murdered their children and thus drove him insane and the nonexistent killer is himself.
In Some Like It Hot, Jack Lemmon, masquerading as "Daphne", gets a marriage proposal from Osgood, an elderly millionaire. Daphne tries to talk him out of it:
Daphne: Well ... in the first place, I'm not a natural blonde.
Osgood: Doesn't matter.
Daphne: I smoke! I smoke all the time!
Osgood: I don't care.
Daphne: I have a terrible past! For three years now, I've been living with a saxophone player!
Osgood: I forgive you.
Daphne: (tearfully) I can never have children.
Osgood: We can adopt some.
Daphne: You don't understand, Osgood ... (ripping off wig) I'm a man!
Osgood: Well, nobody's perfect.
This is what the title of An Inconvenient Truth refers to (specifically, being unwilling to observe something because your job depends on you not observing it).
The Superman example above is Lampshaded in Mystery Men. The Shoveller refuses to believe that millionaire Lance Hunt is really superhero Captain Amazing. He points out to Mr. furious that Lance Hunt wears glasses,while Captain Amazing doesn't. Mr. Furious ripostes that he takes off his glasses when he transforms. The Shoveller responds "That doesn't make any sense! He wouldn't be able to see!"
In Lone Star State of Mind, Jimbo's father keeps trying to set him up on dates with pretty girls, even though Jimbo has been out of the closet for years and everybody else knows. Jimbo even screams, "I'm gay!" to him, to no avail.
In The Hitchhiker's Guide to the Galaxy (at least the novels), Zaphod is literally selectively aware of his own motives, due to having both of his brains surgically altered so that certain thoughts wouldn't be detectable by the brain scans he needed to undergo in order to become President of the Galaxy.
This is also in the movie. It's more of a Hand Wave of Zaphod's two heads because they don't go into specifics.
The basis for the Applied Phlebotinum of the S.E.P. field. Making something invisible is incredibly difficult and requires massive power; an S.E.P. field is easy to make and can be run off a single battery. People can see things under an S.E.P. field, but they don't notice them, because whatever it is, it's Somebody Else's Problem.
Mostly Harmless features a species of bird that is oblivious to every strange thing that happens, like ignoring a fiery spaceship crash. However, they are always shocked by perfectly mundane things. For example, "...And sunrise always took them completely by surprise."
Their train of logic is that an unusual thing only happens once, so it's not worth noticing, as it'll probably not affect them. On the other hand, something that happens every day will affect them, so it's worth noticing.
In Discworld, Twoflower is besotted with the idea of Rincewind as a Great Wizzard (sic), and refuses to realize that he's completely incapable of doing magic. This is far more prominent in Interesting Times, though, as he does seem to exhibit something approaching realization in The Colour of Magic.
Also in the same series, the Duck Man refuses to realize that he has a duck on his head, regardless of how many people tell him so in no uncertain terms. This is more Rule of Funny, though.
Lord Rust is also well known for, as the author puts it, "Erasing unwelcome sights and sounds from his personal universe". This causes problems for him when people like Detritus and the Dean of Unseen University are apparently too large to erase, and hilarity when Vimes takes advantage of it to swear at him without him noticing.
In Making Money, Mr Bent prides himself on his impeccable perception and eye for detail (he can spot a miscalculation with just a glance from across the room) but is oblivious to a female coworker's open infatuation with him. Presumably it's not so much self-denial as it is an inability to expect anyone to have those feelings for him.
In The Secret History, Julian knows every important part of the plot, except for the crucial fact that five of his students killed the sixth one. He wants to believe the best of them, but really, it's not a huge leap to make...
Early on in Quills Window, Courtney Thane's mother writes to him that she genuinely has no idea why his father cut him out of the will right before he died, and Courtney's sentiment seems to be the same. When we find out the reason for this later in the book, it becomes quite obvious that if either of them had engaged in serious self-reflection they would know the reason behind the father's I Have No Son moment.
This is the cornerstone of 1984's Doublethink. Bonus points for the requirement that obliviousness must not only be selective but also instantly switchable — you must completely and sincerely forget whatever you vehemently believed in a moment ago and, if necessary, switch back the next moment — and recursive — you must forget that you've just forgotten something, forget having forgotten that, et cetera.
The mind should develop a blind spot whenever a dangerous thought presented itself. The process should be automatic, instinctive. Crimestop, they called it in Newspeak.
He set to work to exercise himself in crimestop. He presented himself with propositions — 'the Party says the earth is flat', 'the party says that ice is heavier than water' — and trained himself in not seeing or not understanding the arguments that contradicted them.
Crimestop means the faculty of stopping short, as though by instinct, at the threshold of any dangerous thought. It includes the power of not grasping analogies, of failing to perceive logical errors, of misunderstanding the simplest arguments if they are inimical to Ingsoc, and of being bored or repelled by any train of thought which is capable of leading in a heretical direction. Crimestop, in short, means protective stupidity.
Johnnie Rico in Starship Troopers. While he tries hard to paint himself as "just another ape", reading between the lines shows he's pegged as leadership material almost from the start.
This comes to a head when he tells his brevet Platoon Leader that he wants to enroll in Officer Candidate School. He's shocked when the man pulls out the necessary paperwork, already filled out, requiring only Johnnie's signature.
A short story (author, title forgotten) from the 1950s or 60s has a space traveler land on a planet. He encounters a village with two populations, where persons of one population are oblivious to anyone in the other. They dress very differently, so the main character can distinguish between the two. Representatives of both populations see him, because his dress is ambiguous. There is at least one hint that the obliviousness is pretended: Children sometimes interact with children from the opposite population. Parents often find an excuse to spank those children. The main character resolves the issue by turning on a ray that causes everyone's clothes to melt.
The Ministry of Magic in Harry Potter choose not to believe that Voldemort is back in Harry Potter and the Order of the Phoenix despite the overwhelming evidence. They lead the public to believe that all is well and constantly berate Harry and Dumbledore as liars. It's explained that they have a contrived denial caused from how horrible Voldemort's previous reign of terror was. Despite this explanation, many fans interpreted them as Too Dumb to Live. Of course, "it was explained" by the protagonists themselves, and another interpretation is that the Ministery suspected Dumbledore of using Voldermort as a scapegoat to explain his own screw ups at running the school. The Minister of Magic Fudge on the other hand believes that Dumbledore is trying to usurp him as Minister of Magic.
In Book 4 it's briefly mentioned that Petunia, who could spot the tiniest imperfections that could be used for gossip fodder, refused to see that Dudley's obesity had reached dangerous levels (in the book he's compared to a young killer whale). She only sees reason after the Dudley's school nurse sends her a letter about it since the school doesn't stock uniforms in Dudley's size.
Given that by the next book he has lost all the extra weight and is an accomplished boxer, they must have had a fairly limited selection (or he had an inhuman metabolism).
For the whole year, Dudley had been eating what essentially amounted to a couple of grapefruit a day, and with the exercise that came from boxing, he would've lost enough weight to make an anorexic proud.
In the Jin Yong novel Smiling Proud Wanderer Linghu Chong, despite usually being quite perceptive and it becoming glaringly obvious, cannot grasp that his master is a scheming coward who doesn't care one bit for either Linghu Chong or any other of his pupil.
The residents of Valdemar have a magically-induced blind spot when it comes to the existence of magic and the true nature of their Companions. For example, the scholars of Valdemar insist that the ballad of Kerowyn's ride, an account of more or less contemporary events, is meant to be interpreted metaphorically even after the real Kerowyn shows up in Valdemar and becomes one of the Queen's best-known advisors.
In The City and the City by China Miéville, two European cities, Besźel and Ul Qoma, exist on the same spot at the same time, interwoven with each other. Citizens of one city are trained from a young age to "unsee" the other city and its citizens, under dire penalty from a peacekeeping force known as the Breachers.
In Stephen King's IT, the entire town of Derry is afflicted with this, because IT is subtly manipulating them into complacency until IT chooses a scapegoat for them to slaughter. Practically all of Derry sees Beverly being abused by various people and none of them help, one man even calmly going back into his house rather than even scold her harassers. At one point, a man walks into a bar and dismembers a group of men playing cards with an axe. The rest of the patrons don't so much as ask him to leave.
Tobias: You know, Mother Lucille, there's a psychological concept known as 'denial' that I think you're evincing. It's when a thought is so hateful that the mind literally rejects it. Lucille: You are a worse psychiatrist than you are a son-in-law, and you will never get work as an actor because you have no talent. Tobias: Well, if she's not going to say anything, I certainly can't help her.
Rachel of Friends is in constant denial about her true feelings for Ross when she's not with him. On the day before Ross's wedding to Emily, she somehow finally figures it out: "Sure, I like Ross, but feelings are really complicated... maybe I am sexually attracted to him, but I do love him... oh my God." When she demands of Phoebe on why she didn't tell her about her own feelings before, Phoebe replies, "Well, it's so obvious to everybody. It's like saying, 'Gosh Monica, you sure like to clean.'"
Ross asks for no strippers at his bachelor party, and after he leaves Joey immediately asks what kind of strippers they should get. Chandler reminds him what just happened, and he replies "Huh. I chose not to hear that."
The Colbert Report: Stephen Colbert insists that he is completely straight. Evidence to the contrary is dismissed with convoluted excuses when possible, ignored when not (as with the diagram of his brain in which one area was labeled "Repressed Homosexual Urges").
Gul Dukat on Star Trek: Deep Space Nine. His imagined friendship with Captain Sisko escalates to ridiculous levels throughout the series, to the point where he chides Sisko for being so obtuse about his feelings while on the opposite sides of a battle line or in the middle of a no-holds-barred hand-to-hand fight. In fact, you could probably form a whole section on all the things Dukat pointedly ignores. (Although, from what little has been revealed of the Cardassians, that may be how they express friendship, or he may be doing it just to annoy Sisko.)
In Strangers with Candy, the homophobic Principal Blackman is the only one who doesn't know that Chuck and Geoffrey are lovers. At one point he catches them in the school basement and happily accepts the explanation that Chuck is showing Geoffrey the furnace system, even though Geoffrey has his trousers round his ankles.
In Lie to Me, Gillian readily accepts her husband's feeble excuses about having to work late, even though her job is based around the ability to tell instantly when someone is lying.
On Angel Wesley managed to be totally oblivious to Fred's feelings for him in Season Five. This came to a head in an episode when he lectured Angel about the latter's failure to notice Nina's interest, while himself remaining totally unaware of Fred's. She eventually resorted to a Forceful Kiss to get the message across.
In Season Three, Cordelia was this way about Angel's feelings for her. Fred seemed to be likewise re: Wesley's feelings for her, until Gunn later casually mentioned that she knew about them.
Barney Stinson from How I Met Your Mother is almost totally self deluded, not only is he a compulsive liar who believes his own lies, he constantly twists his perception of reality to paint himself and his life as "awesome", no matter how pathetic he actually is. For example, he will invent arbitrary social rules to justify his behavior and claim historical precedents for them, and continually insist they are true, despite their obvious falsehood.
This apparently stems from childhood, when Barney's mother chose to lie to Barney and conceal from him anything that might damage his sense of self worth. For example, when no one came to his birthday party, she forged a letter from the Postmaster General, claiming he had lost all the invitations. This made Barney unable to accept anything that might damage his overinflated ego. Once, when he amiably broke up with Wendy the waitress, he chose to believe she had gone crazy and was trying to murder him, rather than face the fact she simply didn't mind not being with him.
Everything you need to know about Barney can be seen in an episode in the sixth season, Zoe sets Ted up with her attractive cousin "Honey", and Robin and Barney both relate their own versions of the date to Marshall; in Robin's presumably more truthful account, Honey is fascinated by Ted and blatantly flirts with him, while Barney desperately attempts to hit on her and she politely ignores him. While eventually Barney does leave with her, it's only because Ted is much more interested in Zoe and lets him; in Barney's version, Ted bores Honey by droning endlessly about architecture, and she is virtually ripping off Barney's clothes the whole time. When Marshall points out the difference in the accounts, Barney angrily insists his is true.
The entire group is guilty of this and later seasons have them confront this as part of their Character Development. Barney finally acknowledges that Bob Barker is not his father and actually seeks out his real dad. Ted and Robin realize that they do not have a future as a couple and that by remaining roommates they stifle any chance of having serious romantic relationships with others.
Played with in Hannah Montana, Miley mentions that she's kissed before, and quickly backpedals prompting Robbie Ray to say "I love our relationship, you pretend you don't kiss boys, and I pretend I believe you."
In The Mighty Boosh, whenever Vince says or does something suggestive towards Howard (which is quite often) Howard will either walk away or awkwardly change the subject, totally ignoring it
Doctor Who: The Doctor about Martha's feelings for him during Season Twenty-Nine. "It's right in front of me and I can't see it" indeed.
Martha and Captain Jack Harkness both, apparently:
The Doctor: Oh! I know what it's like. It's like when you fancy someone and they don't even know you exist. That's what it's like. (runs off)
Martha:(stares despairingly after him)
Captain Jack: You too, huh?
The Doctor Who New Adventures novel Death and Diplomacy had the Doctor respond to a blatant come-on by a female villain by saying he made a point of being entirely oblivious to such things or getting them noticably wrong, because it saved a lot of trouble.
Guy of Gisborne from Robin Hood chooses to ignore the mounting evidence that Marian is in cahoots with Robin Hood. By the final episodes of season two, he's in complete denial.
A very common theme in Hoarders, where people don't seem to notice they're living in squalor. One episode featured a woman who had a lot of dolls. At one point she picks up a small doll that's the size of a soda can and declares that it doesn't take up any space, completely ignoring the 8-foot-tall mountain of toys in front of her.
Elena from The Vampire Diaries is a darker example of the trope. While she may view Damon as a Jerkass Woobie, Damon has done actions that cross the Moral Event Horizon to her friends including trying to kill Caroline and Bonnie, killing her brother Jeremy (he got better), killing Lexi, turning Vicki into a vampire who had to be staked, and forcibly turning Bonnie's mother into a vampire. Basically, even if you ignore the large number of random people he's killed and continues to kill when he's in a bad mood, he's done enough to the people Elena is supposed to care about that her fondness for him requires mountains of this trope.
The beholders in D&D are like this by design. They have two brains. One is responsible for higher logic. The other hosts emotions and instincts, and is responsible for interpreting the data input from the senses. Thus, if something is against the beholder's beliefs, it will never get far enough to be considered on logical level. Too bad their genetic memory gives them the beliefs of rampant, murderous racists. The only reason they manage to survive at all with such a mindset is that their creator have also found it fitting to grant them innate massive firepower.
At Act I Scene IV, Cyrano fails to notice that the buffet-girl is a Smitten Teenage Girl with him. He is so convinced he cannot be loved, that Le Bret must point out to him this fact (see Oblivious to Love).
In Prototype soldiers will react at the display of the protagonist's Lovecraftian Superpowers or explicit hostility but super-fast runs, super-high jumps, running up a wall or falling from the sky and punching a crater in the pavement will be ignored.
Justified in a Fridge Brilliance manner because the protagonist can slaughter them without thinking about it, and most soldiers would rather keep on living.
Role-players in City of Heroes (and presumably other games) almost require this trope for certain scenarios to take place. For example, there's certain to be more than one (or more than fifty) characters running around who all claim to be the same specific character from mythology (popular examples include Thor, the Devil, and even Santa Claus). If one accepted that all these characters' stories are true, even though they clearly contradict each other, they'd go insane.
Also tends to be a vital tactic in other areas of roleplay: text-based combat (rather than in-engine PVP) often times breaks down into "Bang bang! / OH I dodged! / No, I shot you / no you didn't!" levels of quarrels; Selective Obliviousness is oftentimes the only way to resolve a situation before ending up needing to get mods involved.
Arguably, Harvey Moiseiwitsch Volodarskii from No More Heroes suffers from this in his exit cutscene; he's blinded by Travis' beam katana... And he yells about it being dark.
Masayuki refuses to see the bad in people in A Profile or to distrust his friends. He simply won't notice such things.
Reiji actually does realize how Kyoko feels in Kara no Shoujo. He just thinks it wouldn't be right to start a relationship with her.
Shirou in Fate/stay night seems to have a slight awareness of Sakura's interest in him, but considering he's in denial about his own attraction to her, she's made nearly no progress in over a year and a half of trying.
Junichi in Da Capo is actually perfectly aware that Nemu likes him and has for years. He wasn't just completely dense. On the other hand, she's his adopted sister, which makes things kind of awkward, so he simply did his best not to think about it.
This is actually a pretty strong plot point in Umineko no Naku Koro ni. Battler refuses to believe that a witch murdered everyone. Straightforward enough. However, he also refuses to believe that any of the eighteen people trapped on the island murdered everyone. Not only does he refuse to believe it, he actively rules out the possibility based on the fact that he doesn't want that to be the outcome, even when he acknowledges that the evidence points in that direction. Can you say "cognitive dissonance"?
This being Umineko, the truth of what's going is a bit more... complicated.
Shirogane Sakuya in Hatoful Boyfriend refuses to accept or understand that his brother Sakazaki Yuuya loves him and wants him to be happy, and he interprets everything Yuuya says in the most negative and insulting way he can. Partly this is because his backstab-happy aristocratic upbringing has him suspicious of good intent, partly because Yuuya is a "mongrel" half-breed and he's been taught to hate those of impure blood. Partly it's because Yuuya appears cheerfully oblivious to insults and continues to be friendly just to irritate him. Late in BBL, Yuuya makes a Heroic Sacrifice and reveals all, and Sakuya can no longer be oblivious.
In 8-Bit Theater, Thief constantly denies the existence of dragons. Despite the Light Warrior's direct interaction with several of the mythic lizards, Thief maintains that dragons are extinct. When Red Mage calls him out on it in a later strip while they are being confronted by more dragons, Thief explains that it's "wishful thinking". He just wishes the horrible lizard monsters trying to kill him don't really exist.
In El Goonish Shive, Melissa is so madly in love with Justin, she keeps asking him out even after it is revealed that he is gay. Justin, needless to say, finds this extremely irritating, especially since she is the one who (either directly or "indirectly") blew the secret.
In her case it might be worse than that: in a strip she even stated that "he's just going through a phase".
Earlier in the series (though chronologically after Justin was outed), Elliot pretended not to notice Sarah's feelings towards him, because he was afraid that a romantic relationship with her would destroy their friendship; he may have had Justin and Melissa's ruined friendship in mind, since he'd known Justin for some time at that point.
In Fans!, club president Rikk is utterly oblivious to fellow member Rumy's painfully obvious attraction to him. When third member Katherine gets fed up with this and tries to inform him directly, he exhausts every other member in the club, Katherine included, as potentially having a crush on him. Not once does he even consider Rumy.
In Flipside, Blithe Spirit Maytag has a complete and utter lack of any sense of modestynote As long as she's in her jester costume. Out of it, she's a Shrinking Violet. And an equally complete and utter lack of understanding it in other people. To the point where she's openly baffled when everyone else is upset when their carriage driver is caught using x-ray specs to peep through their clothes. Given the grasp of human nature she shows when she's in Manipulative Bitch mode, this is almost certainly self-justification for her own exhibitionist ways.
Semi-confirmed later on: Turns out that as a child she had almost literally no emotion, barely even reacting to pain. Through conversations with her mother and one or two people that basically "forced" friendship on her, she eventually decided that she wanted to experience life more fully and essentially gave herself Multiple Personality Disorder on purpose; years down the line, she's finally come to realize that the emotionless her, the "shy" her and the "Maytag" her are all equally "her" and - after her costume was sabotaged and she was left naked on stage during a comedy competition - she literally went into exposition mode and explained this to both the audience in the theater and the readers. The whole reason she's "baffled" over other people not living life as "fully" as she does, is that she believes them to be in unnecessary states of self-denial.
Van Von Hunter is sworn to destroy anything evil that he encounters. However, he "doesn't notice" that Ariana Rael, the Child Mage tagging along with him is ungodly evil. The fact that she could destroy him with a thought has nothing to do with why he's not picking a fight with her...
In Misfile, Doctor Upton can hardly have failed to have noticed that his "daughter" appears to have developed some rather severe identity problems, especially considering that it was shouted out at full volume at one point. Despite this, the issue is never raised.
Randy, the tame fox in Faux Pas, is so naïve about sex that it's impossible to think this trope isn't going on. This alternately frustrates and amuses the wild vixen who wants to be his mate. We find out later that Randy does know about "the birds and the bees." But what he knows comes from human television, so anything that strays from Hollywood ideals of dating and romance leave him lost.
In Girls with Slingshots, a Running Gag has been made of Hazel's inability to grasp that lesbian sex isn't just "taking turns with a strap-on." Her lesbian friends have tried to clue her in, but it never seems to stick.
Homestuck: Jake is an interesting example. He pretended to be unaware of his friends' feelings for him so he wouldn't have to give a response before he knew how he felt, but then accepted it without question when Jane claimed that he'd gotten it wrong and that she didn't have feelings for him after all, even when she acted very strangely about the whole thing. However, when he talked with a subconscious manifestation of this thoughts taking the form of Dirk in a dream bubble, thought!Dirk seemed doubtful that Jane had been telling the truth, an idea Jake waved away uneasily, indicating that deep down he probably is aware but just doesn't want to have to deal with it on top of everything else right now, especially after the way he reacted to everything.
Capt. Tagon and Sgt. Schlock from Schlock Mercenary: Tagon tends to have a one track mind and has a hard time dealing with things that don't conform to "shoot it/run from it/run, come back with reinforcements" (at least without someone there to wield a clue bat). Whereas Shlock tends to mentally spin anything he's told into what he wants to believe. (So his orders tend to be simple and specific).note When Petey tells him he won't provide the Toughs with a new ship or assignments because he's trying to remove "a group of sociopaths" from circulation, Schlock immediately volunteers to go hunt the sociopaths down.
In Red vs. Blue Reconstruction, Sarge is unable to understand that Grif is now the same rank as him. Grif actually suggests that he is physically incapable of comprehending that fact.
In King of the Hill, despite his rampant paranoia and suspicion of everyone and everything, Dale Gribble is completely unaware that his wife is having an affair, although it's obvious to everyone else — with the exceptions of Joseph, "his" son, and Peggy (who gets clue-by-four'd later on). Nobody has the heart to tell him about it.
That's because despite his paranoia, he trusts those closest to him — his friends, family, and neighbors — implicitly. And because of howhe'dreact if he ever found out two of his closest friends betrayed him. He's equally oblivious to his father's homosexuality for much the same reasons.
One episode reveals he thought John Redcorn was gay; he does eventually confront the fact that Joseph can't be his son, but comes up with a story involving aliens to explain how he really is.
Invader Zim has two cases: Zim, who refuses to acknowledge that his leaders would like nothing more than his swift and painful death, and Dib, who thinks that exposing Zim as an alien will change how his family and peers think of him, despite plenty of evidence to the contrary.
Panini from Chowder doesn't understand the meaning of the words "I'm not your boyfriend."
Mr. Herriman can spot the tiniest speck of dirt, but he couldn't tell a crudely made decoy of Eduardo from the real Eduardo.
On Total Drama World Tour, Cody. Courtney a bit too, though she was at least suspicious that Duncanwas cheating with Gwen behind her back; when Cody found out he seemed completely shocked, despite the fact that in-universe it's been a common theory they liked each other going back to season two.
Helga: I’m sure my invitation got lost in the mail.
Milo: You live in a fantasy world, don’t you Helga?
Helga: What was that? I was thinking about my hundreds and hundreds of boyfriends.
SpongeBob Squarepants—in perhaps his greatest moment of stupidity—not only completly ignores the words of warning a gypsy woman gives him about the Gremlins-like creatures she sells, but also ignores when it turns into a massive killer eel in favour of chastising Gary for 'bullying the creature' even when he is in its mouth and about to be eaten.
In one episode of Family Guy, Lois' brother, Patrick, is revealed to be the fat man serial killer. Lois refuses to believe Patrick is the killer, despite the several glaring pieces of evidence that point to Patrick, including a half dead fat guy lying in Patrick's room who outright states that Patrick tried to kill him, until Lois sees more and more damming evidence piling up and Brian screaming at her to wake up.
In the episode "The Courtship of Stewie's Father", Lois meets with Stewie's preschool teacher and she shows Lois several drawings Stewie made, which show Stewie killing Lois in various horrible ways. The two women then have this exchange regarding the images:
Teacher: Notice anything unusual in these pictures? Lois: You're right, his father isn't in any of them!
Professor Hamilton in Justice League Unlimited worked with the Cadmus project and attempted to take down the Justice League all because of Superman's invasion of Earth while he was Brainwashed and Crazy and subsequently threatening him, referring to the events of the finale of Superman: The Animated Series. While that is true that Superman threatened him, it's only because Hamilton was being a total prick and refusing to help him save a badly wounded Supergirl because he was more concerned about saving his own ass by not consorting with someone who was considered a felon rather than helping a man he'd repeatedly given aid to in the past no matter the circumstance.
Eric Cartman from South Park is so wrapped up in his own ginormous ego, that he will ignore everything that contradicts his glorified self-image, and what he cannot ignore he will twist in his own favor. On one occasion he frantically strives to avoid a fight with a girl who's mad at him, because if he loses, nobody will think he's cool anymore. When he's forced to fight anyway and loses, other kids assure him that they never thought he was cool and always hated and despised him, so there's no change at all. He thinks that they're just saying it to make him feel better, meaning they care about him, meaning they STILL think he's cool!