History YMMV / KingdomHeartsBirthBySleep

* ContestedSequel: There are a good many people who regard this game as one of the better in the series, if not the best, mostly due to its battle system, the interesting story and refreshing three-POV narrative. However, the game also has many detractors among both fans and critics alike due to combat-related issues (including the lack of enemy knockback, poor combat balancing, and unpredictable boss AI among other problems) and story-related issues that weren't present until this entry in the franchise. Nonetheless, it's usually considered the best out of the myriad of non-numbered spinoff titles released between ''II'' and ''III'', all of which are {{Contested Sequel}}s in their own right, particularly with its ''Final Mix'' version.

** Terra gets the Magic Mirror, an UnexpectedCharacter (since the screenshots depicted ''Aqua'' fighting it instead, something that was proven true) but also Peter Pan,Experiment 221, Braig and is the only one to fight Master Xehanort directly - something not done until ''VideoGame/KingdomHeartsIII''. To say nothing of [[spoiler: Eraqus]], a truly emotional battle.

* DracoInLeatherPants: Vanitas. Although few fans will argue that his actions in-game aren't evil, there's a lot of support for his WoobieDestroyerOfWorlds characterization from the novelization, as well as the idea that [[spoiler:Master Xehanort]] was an abusive master towards him and his motive [[spoiler:to join with Ventus and become whole again]] was sympathetic in a way. There was even speculation that he'll get a redemption arc later in the series.[[note]]Ironically, the series ended up taking the exact opposite route, positioning Vanitas as gleefully and willfully evil even apart from Xehanort.[[/note]] However, some fans will use this to make out Vanitas to be a person who never did anything wrong and really is polite, anxious, desperately craving love while the game contradicts this. In order to make Vanitas more sympathetic, Ventus, Aqua and Terra are pieced to be monsters in fanon works, suggesting Aqua attacked Vanitas without warning with a cheap shot, the trio ruthlessly slaughtering unversed with no remorse, Ventus rejecting Vanitas as a selfish need, not because his very existence was being threatened.

** There's also slight debate on the continuity of the novelization of the game concerning [[spoiler: Vanitas's backstory that paints him in a much more WoobieDestroyerOfWorlds light]]. Some people think that it doesn't make sense when compared to the actual character in the game and enter it under FanDiscontinuity (not hard to do, as the novels are a separate continuity to game canon), while others accept it and think it fleshes the character out more. [[spoiler:Then there's fangirls who take it as an excuse for DracoInLeatherPants towards Vanitas]]. This has only increased when [[spoler: the later games went [[ForTheEvulz as extremely against]] [[CardCarryingVillain this depiction as possible]], even retconning Vanitas' whole origin in the process so that he was a pre-existing being of darkness rather than made from Ventus's heart. Some fans appreciate this, while others hate it and feel it flattens Vanitas' character.]]

** There's also slight debate on the continuity of the novelization of the game concerning [[spoiler: Vanitas's backstory that paints him in a much more WoobieDestroyerOfWorlds light]]. Some people think that it doesn't make sense when compared to the actual character in the game and enter it under FanDiscontinuity (not hard to do, as the novels are a separate continuity to game canon), while others accept it and think it fleshes the character out more. [[spoiler:Then there's fangirls who take it as an excuse for DracoInLeatherPants towards Vanitas]].

* DracoInLeatherPants: Vanitas. Although few fans will argue that his actions in-game aren't evil, there's a lot of support for his WoobieDestroyerOfWorlds characterization from the novelization, as well as the idea that [[spoiler:Master Xehanort]] was an abusive master towards him and his motive [[spoiler:to join with Ventus and become whole again]] was sympathetic in a way. There's even speculation that he'll get a redemption arc later in the series. However, some fans will use this to make out Vanitas to be a person who never did anything wrong and really is polite, anxious, desperately craving love while the game contradicts this. In order to make Vanitas more sympathetic, Ventus, Aqua and Terra are pieced to be monsters in fanon works, suggesting Aqua attacked Vanitas without warning with a cheap shot, the trio ruthlessly slaughtering unversed with no remorse, Ventus rejecting Vanitas as a selfish need, not because his very existence was being threatened.

* GameplayDerailment: Command Melding is supposed to have a degree of blind guessing to it before you collect recipes, but nothing is actually stopping you from making extremely strong Deck Commands with good abilities immediately. Using an online guide breaks the entire system wide open to abuse as soon as you enter the first world.

* MemeticBadass: Vanitas has been propelled to this title, alongside being crowned as a MemeticMolester. However, it is notable that he later went on to get [[LiteralMetaphor booted out]] of this status in ''VideoGame/KingdomHeartsIII'' due to his [[MemeticMutation memetically embarrassing defeat]] at the hands of [[WesternAnimation/MonstersInc Sully]] in that game, catapulting him straight into MemeticLoser territory to the current Kingdom Hearts fandom.

** In a series staple, the absence of {{NPC}}s make some scenes look ridiculous in comparison to the original movies. In [[WesternAnimation/{{Cinderella}} Castle of Dreams]], a Royal Ball where only six people bothered to show up. In [[WesternAnimation/SleepingBeauty Enchanted Domain]], King Stefan's castle, under the Three Good Fairies sleeping spell, is conspicuously empty of any sleeping people apart from Princess Aurora. The most bizarre example is the Olympian Colosseum, where there are a bunch of empty rows of seats where the spectators would be. You would think that would just be it, but after Terra defeats Zack, an invisible crowd cheers with confetti in the air, and when Terra tells Zack that he isn't a hero, Zack reassures him he is "their" hero, gesturing to the empty Colloseeum seats, followed by ''cheering'', implying that there is ''some'' kind of crowd watching the fights. Even ''Terra'' seemed weirded out when he heard the cheering.
** The ending of Terra's campaign is meant to be a somber, and shocking conclusion, but once Xehanort has his goal attained, he starts monologing in an almost NonSequitur manner about the connection between hearts and darkness, even though nobody is really around to listen to him (it's a bit more complicated, but that's spoiler material). It may be hard to swallow that after Xehanort realizes his goal, he just wants to calmly monolog on the existential mechanics of the ''Kingdom Hearts'' series rather than, for example, be elated and in awe that his plan worked.

* EvilIsSexy: Vanitas. [[spoiler:You don't realize this until the end of Ven's story, when he unmasks himself and reveals that he looks ''just like Sora'', except with a more muscular build, black hair, and gold eyes.]]

* SeinfeldIsUnfunny: At the time it came out, part of the reason why Birth By Sleep got a more positive reception among fans and critics compared to the other handheld Kingdom Hearts games was that, due to being on the more powerful PSP hardware, it was the only portable KH game with comparable production values to the mainline numbered games on the [=PS2=]. Nowadays, with the PSP an obsolete platform, most people will be playing the game on a console through the HD collections, so that particular novelty is lost. It also doesn't help that certain aspects of the game are hurt by this transition, such as its very zoomed in camera, which was fine on the PSP, but feels awkward to many people on a console.

* CharacterTiers: The characters are typically ranked in reverse order of what the story encourages you to play. Early-game the tiers are Terra > Ventus > Aqua, with Terra having the best HP and Attack stats of the three to take advantage of the powerful physical commands in most D-Links, while Aqua takes an enormous number of hits just to kill a basic Flood. Worse still, because Aqua can't D-Link with herself, she's the only one to start with no form of immediate access to Cure without use of the Command Board. Late in the game, and especially in postgame, this relationship inverts: the {{Bonus Boss}}es all do such outrageous amounts of damage that relying on HP is a pointless endeavor, with the most viable strategy being to instead abuse invincibility frames to avoid damage altogether. Ventus and Aqua can both have perfect i-frame coverage by spamming their basic Dodge Roll and Cartwheel abilities, while Terra's Slide leaves him vulnerable at the start and end of it, turning Mysterious Figure in particular into an outright LuckBasedMission. [[JackOfAllStats Ventus, in both early and endgame, stays squarely in the middle.]]

** Hades, whether you fight him as Aqua or as a BonusBoss in the Mirage Arena. In both fights he relies on another boss to fight for him, and once his help is defeated, he attacks slowly, with attacks that are easily blocked and punished. However, he has one attack that, while easy to avoid, lasts a good few seconds, leaves him completely invincible, and can be ''spammed with no warning or delay at all.'' Be prepared to waste a lot of time if the AIRoulette isn't in your favor.
** Iron Imprisoner IV, another Mirage Arena BonusBoss, mainly uses attacks you've already seen in his other forms. When he gets low on health, he starts to use desperation attacks that ''look'' very powerful and threatening...but actually aren't and only serve to waste time while leaving the boss invincible, much like Hades.

** When all three stories are completed, you're allowed to save new data for the Final Episode. In the Final Episode, due to a boss waiting there, the battle level for Radiant Garden is higher. However, a glitch randomly caused the battle level for Radiant Garden to increase in any of the three individual stories' save data, from 6 normally to 9 or 10. Battle level determines how strong enemies are in a world and also how much experience they leave, and it happens that Radiant Garden has one of the best LevelGrinding spots in the game anyway. Players were ''hoping'' this glitch happened to them so the Radiant Garden enemies got stronger than they ought to be and rewards more experience, making it quicker to grind up for the {{Bonus Boss}}es.

** Terra is considered the weakest of the trio since his dodge can't be chained for infinite invincibility frames like Aqua and Ven's can. He has the hardest time against the {{Bonus Boss}}es as a result. He is a textbook CrutchCharacter since his immense strength and HP make him a real force of nature in the early parts of the story, but later on he CantCatchUp due to his lack of speed and the aforementioned lack of invincibility frames.

* TheyChangedItNowItSucks: Many fans were not happy with the change in combat engine from ''VideoGame/KingdomHeartsII'' (Command Deck aside) due to the "floatier" feel and even moreso due to the removal of the "revenge number" mechanic, making {{Bonus Boss}}es (and bosses in general) much more random and "[[SNKBoss cheap]]" and less strategic to fight.[[labelnote:Explanation]]In ''KHII'', every boss has a preset "revenge number" that causes them to retaliate against Sora once certain amounts and types of attacks are used against them, leading fans to develop interesting strategies such as specific ability loadouts and purposely abstaining from finishers so as to not cause the boss to retaliate. In ''BBS'', bosses simply retaliate and break out of combos at random, resulting in very tough battles becoming much more luck-based and strategically shallow.[[/labelnote]]

* CommonKnowledge: Terra is best known to be incredibly trusting of all of the ObviouslyEvil villains and easily tricked into working for them, but this isn't true. He's immediately suspicious of most of the Disney villains and just plays along with their plans for a bit, with Jumba and Hook being the only ones to successfully gaslight him.The misconception stems from Terra's interactions with Xehanort, which happen frequently and are integral to making the plot work, and even then, Xehanort purposely makes himself seem sympathetic to Terra by acting as a mentor to him, while Eraqus holds Xehanort in high regard at that point. Ergo, Terra trusting him isn't even that unusual. Additionally? Ventus and Aqua are ''just as'' guilty of trusting the first person they meet whenever they enter a world - they just happen to encounter the heroes and thus the viewers are generally more forgiving - in part because of FourthWallMyopia.

* CommonKnowledge: Terra is best known to be incredibly trusting of all of the ObviouslyEvil villains and easily tricked into working for them, but this isn't true. He's immediately suspicious of most of the Disney villains and just plays along with their plans for a bit, with Jumba and Hook being the only ones to successfully gaslight him.[[note]]Even then, the only Disney villain that gets Terra to cause actual damage is Maleficent, and that was only due to magical brainwashing[[/note]] The misconception stems from Terra's interactions with Xehanort, which happen frequently and are integral to making the plot work, and even then, Xehanort purposely makes himself seem sympathetic to Terra by acting as a mentor to him, while Eraqus holds Xehanort in high regard at that point. Ergo, Terra trusting him isn't even that unusual. Additionally? Ventus and Aqua are ''just as'' guilty of trusting the first person they meet whenever they enter a world - they just happen to encounter the heroes and thus the viewers are generally more forgiving - in part because of FourthWallMyopia.