!!!FridgeHorror:
* The birds eat poultry yet they are all now intelligent. Where do they ''legally'' get poultry from, then? One wonders about their justice system...
* There is a birdspotting club even though all birds are now intelligent. Is this a case of BigBrotherIsWatching? Is it the CovertPervert club?
** It's worth noting that with the exception of a partridge and a quail, all the characters are pigeons. Just as humans do not look upon other mammals equally, it's likely that there are plenty of nonsentient birds left.
** There is a line about a wild swallow caring for her chicks in September, when swallows usually go to live on their own by early summer. Hiyoki and Ryouta speculate that this means ''all'' birds are changing, and Hiyoko observes that the chicks are small, which to players might suggest that they're developing more slowly. Japan's Prime Minister is apparently a shoebill, and a kakapao - a kind of parrot - has just become intelligent enough to be toilet-trained. So the virus that's uplifting birds seems to be affecting different species at different rates.
* You get your Christmas bird ''months'' after [[spoiler: Yuuya disappears.]] Think about what must have been happening to [[spoiler: him in the meantime for the meat to be fresh. He didn't even get the mercy of being quickly dismembered the way our heroine does.]]
* I know you find that other student's ID card in other storylines, so there is some continuity regarding [[spoiler: the infirmary subplot]]... [[spoiler: Does this mean that without anybody to help with his alibi, Yuuya is killed in every storyline but the one where you bail him out?]]
** He is. [[spoiler: If you attempt to invite him to the summer festival, which takes place after the day you would have intervened, you are unable to call him and simply dismiss it as his phone being disconnected. This happens whether you saw the scene in the infirmary or not.]]
*** Except for [[spoiler: Sakuya's extended ending, where Yuuya sends Hiyoko a message at the very end,]] and [[spoiler:Anghel's path, in which Yuuya shows up near the end, [[CrowningMomentOfFunny carrying Anghel in his beak]].]]
*** Considering that, it's just as likely that he ''survives'' in every timeline where he isn't killed, and the later absence is for the same reasons as on his route: [[spoiler: he's busy with missions for the Dove Party and may need to leave so his enemies can't find him. It might be that without Hiyoko working in the infirmary he's more cautious about rifling through things]].
** Speaking of the ID card, unless you wish for [[spoiler: the mad love of a fallen angel]] at Tanabata, [[spoiler: Anghel probably died in captivity except in BBL]].
* In a completely unrelated train of thought, if [[spoiler: the Hawk Party is so bent on you hooking up with birds]], what do they make of your relationship with [[spoiler: Nageki]]?
** Considering [[spoiler: only the pure of heart can see him]] and that if you pick the wrong answer to their final question [[spoiler: he leaves and the Hawk party kills Hiyoko]] they most likely end up [[spoiler: killing her anyway, since they can't see her wooing a ghost]]. Though at that point [[TogetherInDeath it might not be as bad as it seems]].
** You always meet Nageki on the first day. If you don't choose him, you're possibly [[spoiler: leaving him alone, forever, with the glimmer of hope of someone actually being able to see/communicate with him.]]
** If you don't choose to get close to anybody, [[spoiler: the Hawk Party will send someone to kill you in an unexplained manner. And if this game is set after a more severe pandemic involving the [=H5N1=] virus, does that mean that the government is cultivating viruses in order to control its population in a manner similar to SocialDarwinism?]]
* In one of the central backstory events for the BBL route, when [[spoiler:human terrorists massacred all of the bird orphans except for Nageki and Hitori (and also killed Hiyoko's parents when they tried to intervene]], the attack could be considered completely justified in that [[spoiler: Nageki was already infecting humans with a fast-acting lethal virus every time he left the house]].
** [[spoiler: Except Nageki hadn't infected anyone until the Hatoful House incident occurred, and wasn't even aware that his virus could kill humans. [[AllThereInTheManual The guidebook]] explains that Nageki was almost entirely housebound due to his poor health and so never encountered humans. The human extremist group was simply taking a convenient group hostage in an attempt to make their demands heard. They just had really bad luck in picking the house that Nageki lived in.]]
* In the BBL route, we learn that Anghel produces hallucinogenic pheromones, to which he himself isn't inmune (provoking his eccentric personality and delusions), and that those affected by them end incorporated into his fantasies, as demonstrated when Ryouta ends into a RPG battle against him. Now, get back into [[BossBattle the end of Anghel's route]], and lets set the horror of realize that [[spoiler: Anghel and Hiyoko killed Shuu during their collective hallucination, and probably disposed of him while still high]].
** Not quite as horrific as you think. Remember, [[spoiler: Shuu-as-Wallenstein made the classic "you haven't seen the last of me" escape after the battle, swearing to create another hell-bird, and another, until he finally won.]] It actually comes off rather funny when you consider [[spoiler: that he probably came to his senses as soon as he was far enough away from Anghel and wondered what the hell just happened.]]
* Your PC is a savage, though kind, hunter-gatherer who lives in a cave. Yet she has entered a very prestigious school. Meaning hunter-gatherer's life is considered pretty swell for humans in this world.
** If you think about it, it may have been inevitable. [[spoiler: Both of her parents were killed and humans have become an endangered species so it's likely that other humans wouldn't have been able to take care of her or her parents didn't have any other human relations or friends. It also would be difficult for birdies to actually try and take care of a human girl. Her choice of a home may have been why she's still alive in the game. Not a lot of birds actually live in a cave and birds have become civilized enough to live in houses. Her less likely chance of getting exposed to many kinds of birds may be why she's still alive in the game.]]
** In ''Holiday Star'' it's mentioned she lived with Ryouta's family for a while, but then decided to live on her own.
* Kazuaki might have became a narcoleptic because [[spoiler: he is constantly haunted by his dark manifestation of his guilt i.e. dark Nageki and can't sleep through the guilt and constant reminder.]]
** Or it could be [[spoiler: the bleach he puts on his feathers, the constant smell could screw with his brain and make him constantly faint]].
* The second chapter of Holiday Star is an absurd romp, as you might expect when Anghel is a focal character. But it is possible to fail in defense. And if you do, [[spoiler: Tohri's laser]] destroys the school and kills ''all'' of the main cast except for Yuuya, who was out scouting and helping spy teams, and Shuu, out of the country. How bleak, especially since BBL and Holiday Star confirm that the threat of losing his brother is the single thing that can make Yuuya lose his cool.

!!!FridgeBrilliance:
* The teachers have surnames that pun on their species. They're both [[spoiler: fake names, too.]]
* Hiyoko remarks on how she thinks the air conditioning is on, while Nageki says that it isn't. [[spoiler: Ghosts are apparently able to remove heat from their immediate surroundings.]]
* Mourning Doves are named so because the male's calls to attract potential female mates sound [[http://www.allaboutbirds.org/guide/Mourning_Dove/sounds mournful]]. And it turns out that our resident Mourning Dove Nageki gets a [[{{Tearjerker}} very depressing]] scene at the end of his route: [[spoiler: just as he's confessing his love to Hiyoko (or otherwise making those mourning-calls to attract a female mate), this same love is causing his ghostly self to disappear to the afterlife. During this ending Nageki and Hiyoko both regret (aka mourn) how they're not able to spend more any time with each other. Aww...]]
* In the Otome route, Oko San's 'Coo's are translated in a very pretentious, HotBlooded manner with old-fashioned vocabulary, but in the BBL route, they're translated in a more simple, childlike way. At first it appears to be a necessary convention as part of the CerebusRetcon that San is a throwback to before birds were [[UpliftedAnimal uplifted]] rather than a CloudCuckooLander [[TheDitz Ditz]], but then you realise that the narrator of the Otome route is a human girl (who remarks that she has trouble understanding what Oko San is saying half the time) and the narrators of the BBL route are Ryouta and occasionally Sakuya, pigeons. They speak Oko San's pigeon noises instinctively, and think of it as a childish language. But Hiyoko had to learn pigeon speak later in life, probably in a formal setting like a school.
** Wait... does that mean that Oko San is the only one in the game who speaks pigeon? What do the other characters speak, then?
*** [[IncrediblyLamePun Pigeon-english]]
** With this in mind, Oko San's constant use of third-person changes meaning based on who's translating. Hiyoko interprets him as using the "grandiose, self-centered" third-person, while the other birds interpret him as using the childish, immature third-person.
* GeniusBonus: Yuuya is always shown in a semi-stretched position. In RealLife, birds [[ShownTheirWork of his species assume this position]] while doing a [[http://www.youtube.com/watch?v=X_4pkNspN3s mating dance]]. [[HandsomeLech Meaning he is always doing mating dance!]]
* At one point mention is made that fantails didn't get as much intellect when the change happened. However, you meet two fantail characters who are multilingual, verbose, and highly intelligent, which makes it seem like the "fantails aren't as smart" thing was probably just a handwave for [[CloudCuckooLander Oko San]]. [[spoiler: Except, neither Yuuya nor Sakuya are pure fantails.]]
** And why didn't the purebred Fan-Tails get as much intellect during the uplift? The inbreeding to produce the purebred Fan-Tails has led them to have degraded genetic vitality. Fan-Tails are a variety of Rock Dove produced through humans' artificial selection. In the pigeons fancier community, Fan-Tails are bred and shown off in pigeon shows just like purebred dogs are in dog shows. Pedigree lineage is [[http://en.wikipedia.org/wiki/Inbreeding_depression notorious]] for causing genetic defects and health problems in the long run. This decline in genetic vitality may have led a hand in why purebred Fan-Tails aren't as intelligent as mixbreeds, which have the advantage of [[http://en.wikipedia.org/wiki/Hybrid_vigor hybrid vigor]]. If Okosan is indeed a purebred Fan-Tail, this may explain his CloudCuckoolander nature.
** There are several different kinds of fantail. The various show fantails are more fancy, poor fliers, and elaborately bred. Garden fantails come from more diverse stock and are well suited to living outdoors with minimal maintenance.
* In BBL it's revealed that [[spoiler: Yuuya's stepfather had to murder Yuuya's father to marry Yuuya's mother.]] And why did he have to [[spoiler: murder him]]? [[spoiler: Pigeons are monogamous, or paired up for life. Therefore Yuuya's stepfather ''had'' to murder his competitor to get to Yuuya's mother.]] And it's common for male pigeons to [[http://www.youtube.com/watch?v=NKJmHURxPTM fight]] to be alpha-male anyway, whether in captivity or in the wild.
* The glass is all ''ridiculously'' [[SoftGlass breakable]]. Nageki once breaks the library door's glass, and Anghel crashes through windows wherever he goes. They are apparently large birds, but still smaller than humans, and glass breaking is treated as casual. Maybe everything is ''built'' with SoftGlass because un-uplifted birds smack into it so often.
* The otherwise stoic bird portraits for the bird characters allows the player to imagine any emotion that those characters may be experiencing at that moment. This is because realistic birds ''can't express human-like facial emotions'', such as smiling, scowling, or raising/lowering of the eyebrows, due to their inherent bird anatomy!
--->'''Angie Gallant''': ''[[http://www.quartertothree.com/game-talk/showthread.php?t=67529&page=15 (referring to the upset Ryouta's photo)]] "I don't know if it's because of the sad piano music or because I have well and truly lost my mind, but that stock photo of a pigeon just looks so sad right now."''
** Likewise, all the ICPSS human-style portraits of the birds are {{Bishounen}} because traits like elaborate plumage and bright colors are masculine for birds, but would be read as feminine by humans.
* Common bird species such as pigeons have become uplifted quicker and more intensely than endangered species such as kakapos. This is because these birds have large enough populations to allow genetic diversity to propagate the favorable traits of higher intelligence and sentience bestowed by the virus. On the other hand the critically endangered [[http://en.wikipedia.org/wiki/Kakapo kakapos]], which as of February 2012 have only 126 living individuals, has just had an individual toilet trained in the ''Hatoful'' universe. Additionally, the more intensely uplifted bird species have greater contact with humans in general, thus allowing more contact with the uplifting virus. For example, [[http://en.wikipedia.org/wiki/Rock_Dove Rock Doves]] are commonly seen as pests in many urban areas, or otherwise humans can domesticate and breed them like the Fan-Tailed varieties. [[http://en.wikipedia.org/wiki/Mourning_Dove Mourning doves]] are the most common wild dove species in North America, and thus they are commonly hunted in their respective breeding season. As seen in the the Torimi Cafe sidequest [[http://en.wikipedia.org/wiki/Budgerigar Budgerigars]], [[http://en.wikipedia.org/wiki/Java_Sparrow Java Sparrows]], and [[http://en.wikipedia.org/wiki/Barred_Parakeet Barred Parakeets]] are uplifted, and those species are commonly kept as pets. Even [[http://en.wikipedia.org/wiki/King_Quail King Quail]] and [[http://en.wikipedia.org/wiki/Chukar_partridge Chukar Partridges]] are either commonly hunted by humans or are otherwise kept in captivity and bred. As for [[http://en.wikipedia.org/wiki/Luzon_Bleeding-heart Luzon Bleeding-Heart doves]], the reason why the one we see in-game is so unhinged is because as of December 2012 this species is Near Threatened, since they are endemic to Luzon Island of the Philippines and they are often poached for either for their meat or for their distinctive plumage in the pet trade. However, a breeding program in Australia will increase this species' population size and allow the birds to be legally available in the pet trade. Overall, it's a bird species' population size and proximity to humans that determines how uplifted they will be in ''Hatoful Boyfriend''.
** Except the Prime Minister of Japan is a shoebill stork. It's mentioned when uplifting comes up that it takes time for a species to adjust into society, and they'd need to be adjusted to rule a nation. There are at most eight thousand shoebills in the wild right now, and since they're five-foot-tall solitary predators they're not exactly domesticated.
* The best beans to give to Yuuya or Anghel for Legumentine's are the bitter black beans. Know what else is bitter, black, and a bean? Coffee beans. The bitter black beans are the best ones to give to Yuuya and Anghel because their endings require them to go into dangerous situations: [[spoiler: Yuuya must flee Hawk Party agents and Anghel must RPG-battle the evil tree Himnesia]]. Upon receiving them, Yuuya even mentions how much energy these beans will give him for the nights ahead. However, caffeine is toxic to animals; [[AWizardDidIt perhaps]] the uplifting gave the birds human-like caffeine tolerance alongside human-like intelligence?
* Anghel's rather bizarre outfit is appropriate for someone who is [[spoiler: constantly [[MushroomSamba tripping]]]].
** Is it any surprise that an amateur mangaka dresses like a manga character?
* In ''Holiday Star'', the heroine mentions being friends with the Conductor. [[spoiler: The Conductor is Death. Considering how easy it is to get a bad ending in Hatoful, and how aware of the fourth wall the heroine is, she must visit him a lot.]]
** FridgeHorror: This would mean she's aware of all the bad endings she's gotten.
* The backstory involves [[spoiler: much of humanity dying off due to bird-borne illness,]] and human scientists coming up with "Operation Carneades" to [[spoiler: kill all the birds before the human race is wiped out.]] It [[GoneHorriblyWrong doesn't work as planned]], of course, but where does the word "Carneades" come from? A [[http://en.wikipedia.org/wiki/Plank_of_Carneades thought experiment]]. If there are two drowning sailors and a plank that can only support one, and one keeps the other from clinging to it and is later rescued, is it considered murder, or self-defense?
* When looking at the shrine vists before plays through Holiday Star [[spoiler: Kazuaki]] seems VERY out of character and can cause some confusion by talking about [[spoiler: Hitori as a seperate person]]. Looking back after playing the last two chapters does the player realize why that is: they found a casual BBL spoiler/ foreshadowing moment caused by the scene being set in an alternate universe like Nageki's visit, maybe even the same one. [[spoiler: The Kazuaki seen at the shrine is the REAL Kazuaki, who became a literature teacher, as opposed to Hitori, the math teacher who stole his identity after his death to avenge Nageki. Since Nageki never died Hitori never drove Kazuaki to suicide.]]
* Kazuaki's route ends with you giving him [[spoiler: a photo with a scribbled-out face and asking about it. He tells you this was the photo of the only person he's ever loved whose loss, he thought, rendered him unable to love again. But now, that he's found you, he has burned the photo, letting his love go and thus becoming able to love you.]] At first, this makes him sound just like a big emo kid. But if you consider BBL route, [[spoiler: the photo is most likely of his long-dead beloved foster brother Nageki. After his death, Kazuaki turned into a psycho whose only thoughts were those of revenge. He believed that Nageki's shadow lived in his heart and demanded revenge, while in reality it was the Dark Nageki he made up for himself. The real Nageki only wanted him to have a normal life like any other. So, the words about "letting go" probably meant destroying the Dark Nageki, giving up on revenge and becoming a regular person instead of the murderous psycho we see in BBL.]] In other words, [[LoveRedeems your love redeemed him.]]
* If you go to the library instead of going home or helping Kazuaki on Anghel's route, Anghel has one of his usual conversations with Nageki, who is stupefied beyond ability to respond. [[spoiler: Unsurprising, since this is the first time someone other than Hiyoko has shown they can see and hear him despite his being ''dead'' and Anghel seems to know stuff about him from ''before'' he died.]]
* [[spoiler: In the Bad Boys Love route, during Yuuya's death scene, Sakuya calls him by his first name, Yuuya, as opposed to calling him Sakazaki like he used to. In Japan, you only call someone by their first name if you're close to them. Meaning that the first time Sakuya felt close to Yuuya was as he was dying!]]
** Also, near the end of BBL, there are a few instances where Sakuya calls Ryouta by his first name instead of calling him "Kawara". Meaning that the events of BBL have made him closer to Ryouta, too!

!!!FridgeLogic:
* How are you able to answer "Yes" [[spoiler: after Shuu has cut your head off and is carrying it around with you?]]
** Someone on the LetsPlay thread came up with an answer to that: [[spoiler: He's not carrying her. She's been incorporated into Labor-9 in this timeline, too.]]
** It could also just be in the same manner that [[spoiler: Hiyoko's spirit is able to communicate with Ryouta in the ending of the Bad Boy's Love route.]]
** I just assumed that [[spoiler: she didn't "say" anything-- Shuu was just deluding himself into thinking she did. Relatedly, my question is: How did Labor-9 make those breathing sounds (identical to Hiyoko's dying gasps) if nothing was left of Hiyoko but her brain?]]
** Another person on the Let's Play thread interpreted "yes" as [[spoiler: Hiyoko's head bobbing up and down in the jar.]]
* How can you [[spoiler:be killed by a small bird?]] You're a human, far bigger then him.
** It's outright said why: [[spoiler:You're frozen with fear, he has a cleaver, and it's implied a part of you wants this to happen.]] A better question would be how [[spoiler:he's holding said cleaver.]]
*** [[spoiler: [[CompletelyMissingThePoint With his left wing, of course.]]]]
* The whole idea of romance between a human female and a male bird. Just how is this supposed to work? For reference, when Yuuya [[spoiler: is cooked]], Hiyoko notices that he is approximately the size of a turkey. So, [[spoiler: advanced]] birds became bigger, but still not human-sized. Not to mention, that human reproductive organs are different from those of birds. And while we are at InterspeciesRomance, what about Shuu and [[spoiler: Dr. Kawara]]'s relationships? One is a partridge, the other is a [[spoiler: pigeon]]. Even if they got together, how would that work out?
** The same way human lesbians do? You don't need a penis and an orifice to stick it into to have a sex life. It just takes a little more imagination.
* The oldest Pigeon Blog entry dates to 2005. The departure point for this [[AlternateHistory alternate history]] is between 1918 and 1997. The latest point in time [[FanNickname Operation Virus the Fuck out of Everything]] would have begun would have been 1999; by the twenty-eighth of November in 2005, Brian would just have the intellect of any average pigeon at that point.
* The good ending for Yuuya's route ends with [[spoiler: you running away together with him and becoming a spy for the Dove Party, like him]]. Oh, I'm sure Hiyoko will make a fine [[spoiler: spy]] being one of the few surviving humans in a world overtaken by birds...
** It might still work, [[spoiler: unlike the Hawk Party, the Dove Party believes in peaceful co-existence with humans, with that in mind it is possible that even though the birds are definitely in charge they may have or at least be willing to consider having a few sympathetic humans working for them too. Hiyoko's own parents were peacekeepers and negotiators between humans and the ascended birds. Also there are certainly at least some humans that hate and resent the birds for having become the dominant species, so maybe in Yuuya's route, if she isn't following a similar role to her parents for the Dove Party, Hiyoko could be spying on other humans and reporting back any acts of hostility or plans of violence back to the Dove Party so they can try to defuse the situation before it escalates?]]
* While it's played for laughs, one moment in [=HolidayStar=]'s radio sessions does bring up a few questions - namely, the reveal that our hunter-gatherer girl's den once got hijacked by jackals and after fighting them, she was welcomed into their tribe as a brother. So, did ''jackals'' become sapient too? How? Did this happen to ''other'' animals as well? And perhaps least importantly, what are wild jackals doing in Japan?
** According to the manga, wild water buffalo live in Japan, too.