Why is Yosuke teamed up with Hazama (and potentially Terumi)? Not only do they both use a type of throwing knife, Yosuke's Ultimate Persona is Susano-o. Terumi's true form is Susanoo.
Ruby teaming up Nu-13 may seem odd at first, until you realize that it is possibly a Shout-Out to Ruby's friendship with Penny - who was said to be directly inspired by Nu herself.
Ragna and Hyde teaming up makes sense when you consider that out of all the four series represented thus far, BlazBlue and Under Night In-Birth are the only two to have started out as fighting games from the beginning, whereas Persona initially started out as a JRPG while RWBY is an anime-esque web show.
Yu Narukami has some of the least combative, and in fact some of the most cordial team intros between franchises shown thus far. Why is that? Recall how he nurtures his power. Seems all that time creating bonds has become habit for him.
One might wonder though why he seems to get along well with Hakumen and Tsubaki, two characters who have a very strong association with Justice. Well, remember who is the Justice Arcana in his home world? It's someone precious to him that you shouldn't touch.
The overview trailer along with other promotional materials tend to pair up the base roster characters who have many similarities with one another and/or who serve as Foils to each other. Case in point:
Ragna the Bloodedge and Ruby Rose: Both of them have been paired up together as a team in almost all of the game's promotional materials. Both of them are scythe-wielding protagonists clad in red and black whose series have fantasy-like settings, and have lost a loved one (Ragna losing Saya, Ruby losing her mother Summer). But while Ragna was an older brother, Ruby is a younger sister.
Yu Narukami and Hyde: Like with Ragna and Ruby, both of them tend to be paired up a lot as a team in promotional materials. Both of them are kind, katana-wielding ordinary high-school students whose series have modern 21st century settings but with supernatural elements added to them (the Midnight Channel for Yu, the Hollow Night for Hyde). But while Yu is calm and leader-like, Hyde is brash and confrontational.
Jin Kisaragi and Weiss Schnee: Both have powers over ice and serve as the rivals/Foils to the main characters of their series. But while Weiss and Ruby sort things out very quickly, Jin and Ragna's rivalry never really dies out.
Yosuke Hanamura and Linne: Both of them are Fragile Speedsters who serve as the deuteragonists/lancers to their respective series' protagonists (although story-wise, Hyde comes off more as Linne's Lancer if anything). Their personalities also heavily contrast one another as while Yosuke is jovial and cheerful, Linne is stoic and straight-faced.
Makoto Nanaya and Chie Satonaka: Both of them are cute, action-oriented females who prefer fighting at close range. But while Makoto primarily uses punches, Chie primarily uses kicks.
Iron Tager and Waldstein: Both of them are the token grappler characters from their home series, are the two largest characters in the cast, are actually much kinder and gentler than their menacing appearances suggest, and primarily serve a female character who is smaller in stature than them (Kokonoe for Tager, Linne for Waldstein).
Ruby's pronunciation of Ragna (RAG-na instead of ROG-na) is this when you realize Remnant's pronunciation of names are weird. Weiss' name is technically suppose to be pronounce with the W sounding like a V but in Remnant all letters in a person's name sound like they would be in English. So "Veiss" becomes "Weiss", "Zvei" becomes "Zwei" and "ROG-na" becomes "RAG-na."
It could also be rooted in Ruby's noted difficulty in pronouncing names unfamiliar to her, which came up numerous times during the fourth volume of her show.
Interestingly, in the story mode, she pronounces Hazama with stress on the second syllable instead of the first as it is usually pronounced in the dub. She actually seems to be pronouncing the names the same way the default announcer does, rather than how the dub typically pronounces them.
Weiss tries to order Nu-13 around in their interactions, only for her to be met with subtle defiance from the Murakumo Unit. Weiss comes from Atlas, which mass-produces robots built for combat, so it's safe to assume that Weiss's haughty attitude is a result of her assuming that Nu is just another mindless robot built for battle, which is understandable considering Nu's normal behavior and how Weiss has yet to see how Nu acts when Ragna is around. Ironically, the one robot in Weiss's world that isn't just a mindless machine, Penny Polendina, happens to be based off of Nu-13 herself.
Weiss also refers to herself as the 'leader' of their team-up, which leaves Nu mildly confused. In her world, Weiss initially felt that she'd been snubbed for the leader role of her team that she felt was hers.
In EpisodeBlazBlue, Ragna and Gordeau fight Ruby and Blake with one very distinct advantage neither might be aware of. Their Soul Eater and Snatcher abilities damage and absorb enemy souls, which just so happen to be the very thing which powers the RWBY cast's Auras and Semblances.
Blake may fight well by herself, but RWBY shows that she and her teammates fight better together, while Ragna is a literal One-Man Army who has rarely relied on others to fight his battles.
Blake's powers rely on a finite resource (her Aura) and limited stamina all tied to her soul, while Ragna has no issue with resource management (Seithr is commonplace in the BlazBlue universe) and can fight endlessly while he absorbs the souls of others.
Lastly, there's the simple fact that Blake has never fought anyone on Ragna's paygrade, like Take-Mikazuchi, Nine, Hakumen, Azrael and Terumi. All of these combined explains Ragna's flippant attitude while Blake complains about trying to keep up with him, and considering that he is likely the most powerful being on the roster, it makes the comparisons in power between BlazBlue, RWBY and the other series a lot more obvious.
When a match is entirely comprised of Persona 4 combatants, either "Shadow World" or "Pursuing My True Self" plays, and both of those songs are the most peaceful on the soundtrack and aren't exactly first picks to put in a fighting game created by Arc System Works of all people. However, remember that as of the pre-EVO roster, the Persona cast are all close friends with one another, and the relaxing nature of their universe's VS themes reflects that.
Related to this, the Persona 4 Arena story has Yu exclusively fight with Yosuke, Chie, and Yukiko (barring the team up with Ragna near the end) while the other 3 protagonists have a more diverse partner selection because the P4 roster are True Companions while the BlazBlue and UNIEL cast have more Enemy Mine or Teethclenched Teamwork moments due to the various factions and agendas and RWBY more or less split up to either accommodate the Tag Battle rules and/or to cover more ground.
Why does Carmine's dub voice sound less like someone genuinely menacing and psychopathic and more like a high school bully trying to be edgy? Because really, besides his bloodthirsty streak, that's all he is, as shown in EXE: Late[st]'s story mode: a mildly unhinged, but otherwise average Jerkass moody teen who beats up people he doesn't like, and something of a Butt-Monkey besides.
Speaking of Carmine, Hazama finds him to be quite a bit similar to Yuuki Terumi in the story mode. This goes beyond their shared blood-lust, crass attitudes, and maniacal laughs: Central Fiction ultimately reveals that Terumi, really Susanoo, is at heart just Amaterasu's younger brother who REALLY resents having to serve her. His evil plan pretty much boils down to destroying all of her creations just to piss her off. The reason they're so similar is because they're both basically bullies who have nothing better to do with their powers.
Jin surprisingly getting along with Orie in their pre-fight interactions (only in the English version, however) makes sense considering that Orie works for the Licht Kreis, an organization that serves to protect people from the Hollow Night through enacting justice and order, and Jin possesses the Power of Order. They share similar virtues, so naturally they can cooperate with each other. This doesn't even get into the fact that Orie's personality is similar to Tsubaki Yayoi, arguably the one person in the BlazBlue universe he respects the most to the point where he'd likely treat Orie similarly. Similarities like that can also be found with Mitsuru, another character he seems to respect enough in his intros.
Yang says that a bucket (trash can) suits Yosuke, and says he should try posing it. While that might seem like an insult, Yosuke does pose with said trash can in the opening animation for Persona 4: Golden.
Yu has a palette based on Joker in which taking aside their roles as the protagonists of their games, Joker purposely was destined for a Contrasting Sequel Main Character for Yu becoming his Foil in the process.
Yosuke has a skin based on Ryuji Sakamoto who was already a huge Composite Character between Yosuke and Kanji.
Chie has a palette based on Makoto Niijima. Both Makoto and Chie specializes in close-quarterscombat, have an avid love for action films, gets scared witless by "spooky" stuff, and have a female best friend who's a Girly Girl to her "Tomboy" while possessing some amount of Les Yay with each other. Similarly the Social Links for both characters end with them resolving to become police officers.
Yukiko has a palette based on Ann Takamaki. Both of those girls have a similar moveset in their orginial RPG games as they are both specialized in healing and fire skills.
Kanji has a palette based on Yusuke Kitagawa. As mentioned in Yusuke's character page, he was already a pretty huge Foil of Kanji as they have the same Arcana, similar love for the arts, different looks, and a different relationship with the person who has raised them. They even have the same English voice actor.
Naoto has a palette based on Morgana. Both characters have androgynous features to them with Naoto being a Bifauxnen while Morgana has a female voice despite him identifying as a boy. Not to mention both of their character arc revolved around accepting who they are as Naoto accepts that she is a young female detective and Morgana accepts that he was never human to begin with.
Aegis has a palette based on the Velvet Room twins. As the only Persona 3 character that shows up in the story mode in comparison to all of the other Persona 4: Arena characters that came directly from Persona 4, it makes sense for her to have a palette not based on an actual party member from Persona 5.
Relating to this, Labyrs also has a palette based on the Velvet Room twins. This makes sense since Justine and Caroline are "sisters" much like Labrys and Aegis.
Mitsuru has a palette based on Haru Okumara. Haru was intentionally destined as a Foil thanks to both of them having the same arcana, similar backgrounds, different personalities, and different reactions to the death of their fathers.
Akihiko has a palette based on Futaba Sakura. This is more of an Irony than anything as since Akihiko was the resident Blood Knight of the Shadow Operatives while Futaba is the only member of the Phantom Thieves that does not participate in battle. That being said, they both secluded themselves for their own interests, Akihiko spent time away from the Shadow Operatives to train and Futaba shut herself in her room. They also both have No Social Skills.
Despite fan expectation, Yang doesn'tdeliver any puns in this game. This is actually consistent with her characterisation in her home series, where she's only made one pun in the show, despite fan interpretation of her character often making it one of her only traits. It also makes sense when considering that this game is made in Japan, where that interpretation of her being a Pungeon Master would be less prominent, as it primarily comes from the fact that Yang's English VA, Barbara Dunkelman is a notorious Pungeon Master (though again, this doesn't extend to how Yang is characterised in the show, and in fact the one pun she's made was actually a Fandom Nod to Barbara's reputation).
Hyde, Linne, Waldstein and Vatista's No. 13 palettes are all references to Steven Universe, a story about a boy who is a Naïve Newcomer to a group made up of ancient, immortal warriors. Hyde is a Naïve Newcomer, and Linne, Waldstein and Vatista are all ancient, immortal warriors.
The same also applies to Merkava, however who is a Void, but perhaps Vatista still spares him due to how he Was Once a Man.
The reason why the Persona 4 Arena characters can use their Personas in the Phantom Field: it's stated a few times that the Phantom Field was created from the dreams of System, very similar to how the dungeons in Persona 4 work being built out of the person's repressed desires and emotions.
Why is Episode BlazBlue one chapter longer than the others? Because despite playing the fight out in gameplay, Ragna actually fled from Nu, Aegis, and Vatista, and thus the System didn't get adequate battle data from them, and thus couldn't achieve her true form without throwing an extra fight at Ragna.
Blake's interactions with Merkava are in line with the fairy tale she is based off of, especially the Disney version where she and Belle are book loving girls who see the noble and kinder side of the titular Beast and are willing to protect him.
While many people are upset that Teddie and Rise didn't make it to the original roster of 40 characters, it can make some sense given how they never were supposed to participate in the original P-1 Grand Prix tournament in the first place (With Teddie technically only joining the tournament after he fought the P3 characters in his story mode). While you can make the same case for the Shadow Operatives, it should be noted that none of them appear in Episode P4A (With Aegis be the only Shadow Operative to actually appear in story mode at all). However, this has since been reflected that Teddie has been added to BBTAG since version 1.5 and that he'll have some sort of interaction in the "Episode Extra" scenario in version 2.0.
RWBY is very much emblamatic of The Last of These Is Not Like the Others in that it's primarily a Western web show whereas BlazBlue, Persona, Under Night, Arcana Heart, Senran Kagura and Akatsuki Blitzkampf are all Japanese game series. Only reading through how it and BlazBlue (and probably by extension Akatsuki Blitzkampf) are similar in that they lean more towards fantasy worlds whereas the other four are more grounded in modern-day Japan led to one other realization as to why RWBY is still the odd series out beyond its medium: it's the only one here that doesn't take place in our real world, as at the very least the BlazBlue is set 20 Minutes into the Future, albeit being too far ahead into the future where it bears little to no resemblance to what we recognize as Earth to begin with.
While Blake is rather distrustful of Hyde in both Story Mode and Versus Mode, that may be because he reminds her too much of Adam for her liking. Hard not to see why, as both wield red katanas, wear all black, have a pretty edgy personality, and have a powerful attack that involves slicing an opponent with a wave of red energy that can disintegrate them from existence.
Of course Neo would be teamed with Hazama in her trailer, considering how similar he is to Roman.
The coolness factor of a crossover of seven different franchises is undercut by the fact that many of the BlazBlue characters are far and away the most powerful in the crossover, that they very often use lethal force when they're fighting (especially for Astral Heats) and that the Persona 4, RWBY, some of the Under Night In-Birth casts and even characters from Arcana Heart and Senran Kagurais comprised of middle-schoolers, high-schoolers and first year college studentsnote The RWBY cast attend Beacon, which in their show is more akin to a prestigious university than it is a high school - as students begin attendance at age 17/18 and finish their education at 21/22. Ruby herself is definitely high school age, but got pushed ahead two years on the recommendation of Beacon's headmaster, Ozpin. This is especially true for the likes of Hazama, Nu-13 and Azrael.
This comes up in Episode Under Night In-Birth. It turns out Azrael's sheer power and bloodlust mean he alone can attack others without a partner. He attacks Weiss and she is unable to fight back because of the same rules that Azrael breaks (and not even SYSTEM can restrain him). If Hyde wasn't there to intervene, there's no question that Azrael would have beaten Weiss to death and probably would've moved on to Carmine, who, despite his crude and borderline Ax-Crazy attitude, is still a kid.
Also comes up in Episode Persona 4 Arena where it's stated multiple times that the Investigation Team wouldn't have stood a chance without their Personas.
Noel, Chie and Yukiko are all in the same game, and if Ragna and Makoto's testimony is evidence, Noel's cooking has gotten not one bit better. Heaven forbid these three girls occupy the same kitchen...
Also, if you play Persona Q: Shadow of the Labyrinth, you might remember Naoto trying to have all of the other P4 girls as well as Fuuka make "Mystery Food X: The Final Edition" which took out a FOE in one hit. If Rise and Fuuka ended up being NPC characters in this game, then if you add in Noel's cooking, you might have to experience something even more deadlier than that.
As noted in the Shout Outs page, Weiss has a palette swap based on Pyrrha Nikos. Now recall what Cinder Fall did to both of these girls on two separate occasions as of RWBY's 5th season.... (But at least Weiss managed to survive her impalement.)
As explained under her character entry, one of Vatista's win quotes provides an explanation for what an Autonomic Nerve is, as her home game does not: effectively an Autonomic Nerve is a kind of haemonculus created by implanting a human soul into the body of an artificially created doll. However she isn't specific as to whether or not these souls are newly-made and tailored for the dolls or, more horrifically, that these souls were taken from already living people. Worse, in her home game it is suggested that ten thousand Autonomic Nerves were created originally. If the former case it's just a matter of a lot of creepy living dolls; if the latter case, well, the creation of the Autonomic Nerves was an act of human experimentation and transmogrification that flies well over the Godzilla Threshold and well into Moral Event Horizon territory.