Why is Kanji the only character who's using a joke weapon instead of one of his proper weapons? Because Kanji is the only character who did not come into the TV world prepared, so he had to use what he could find.
Just noticed this game's disc is a darker shade of yellow than the original's PS2 disc. Then I realized it's because the P4 story just became Darker and Edgier.
This doesn't apply with the European release, which instead has a blue backdrop.
The game's story mode is really easy for a fighting game. The final boss in particular is no SNK Boss, and is a pretty serious Anti-Climax Boss. However, it makes sense this would be the case in story mode since this is a continuation of a turn-based RPG's story… it would be pretty cruel to Persona 4 fans that they can't continue their story without adapting to a whole new genre.
This can be applied further. The game as a whole is much easier to learn and play than ArcSys' other games.
Why doesn't being forced into Fighting Your Friend affect the Shadow Operatives as much as it does the members of the Investigation Team? They already went through this back during the events of The Answer, whereas it's uncharted territory for the Investigation Team.
They've also known each other for a number of years; whereas with the sole exceptions of Yukiko and Chie, the Investigation Team haven't been friends for that long — Yosuke's only known Chie and Yukiko for around a year and a half; Yu and Teddie have only known the three of them for just over a year; and the rest of the group joined up over the course of the following year.
The male Yasogami uniforms have a roman numeral on the collar signifying what year the wearer is in — in Persona 4, Yu and Yosuke had a "II" while Kanji and Naoto had a "I". In Arena, Yosuke has a "III" and Kanji has a "II", but Yu still has a "II"… because he's no longer a Yasogami student and is using his old second-year uniform.
Shadow Labrys is a bit weird, considering she fights while still using her humanoid form and alongside the Asterius Shadow as opposed to transforming into a new monstrous form. However, remember that she is based on Labrys' desire to be normal, so her fighting alongside Asterius like the Investigation Team and Shadow Operatives do with their Personas may reflect that desire subconsciously.
It's also possible that it's because, unlike the Investigation Team, her Persona had briefly awakened before being thrown into the TV. As the Persona wasn't fully awakened when Labrys was thrown, her Shadow was still able to manifest.
Another factor could be that Labrys was developed with intention of summoning a Persona. Since the scientists thought that a weapon with an ego shouldn't have feelings, it would make sense that her personification of pain and suffering would manifest itself as a perversion of a Persona-user.
Still a third possibility presents itself in the form of Metis, a character introduced in Persona 3 The Answer. At first introduced as Aigis' "little sister" it eventually comes out that Metis was Aigis' discarded desire to be human. While she is never positively identified as a Shadow, her existence is rather similar to the repressed selves of Persona 4, although she is rather friendly toward her other self. And notably, Metis also used a Persona much like Shadow Labrys seems able to. Perhaps it is a trait inherent in Kirijo group robots that even their shadow selves can develop a Persona?
Why, when story mode clearly uses "The Carnivore Who Discarded Womanhood" as Chie's Red Baron, does the game still use "The Spunky Dragon With Deadly Legs" in it's place? Chie was the one who was most displeased with her tagline.
When battling the Eerie Voice/Malevolent Entity during Story Mode, the theme that plays is The Almighty, the same one used for the battle against Persona 4's Ameno-Sagiri. How is this relevant? Ameno-Sagiri served as the Final Boss of the story, but take note: this was only if the player did not do battle with the True Final Boss Izanami. This obviously pointed to the fact that the story isn't over yet.
Why is Yukari wearing her Pink Argus costume from Phoenix Ranger Featherman Victory? If someone saw her fighting Shadows and tried to tell people, no-one would believe that Pink Argus actually was running around fighting crime.
The actual reason is, apparently, that she got picked up on set without taking any time to switch out of her costume.
The two versions of Sho have differing Arcana because the differences between them are night and day.
Taking this into account, this also explains why Shadow Aigis is nothing like Metis, who in contrast represented Aigis' suppressed human side.
Mitsuru and Akihiko both can use specials even when their Personae are broken, in contrast to the other characters. This makes sense because unlike the others, they both have had years of training in what they do best (fencing and boxing respectively)!
In Ultimax every character, from Narukami, to Aigis have a shadow counterpart as a playable character. However, several characters don't, those being Elizabeth, Marie, Adachi, Sho (both verisons), and Margaret. The reason this is so important is that all of these characters are bosses or major antagonists who don't have a Shadow. Elizabeth and Margaret are hardly human, Adachi was shown without one and it's implied he never had one, Marie is a Physical God, and Sho is the Big Bad of the game, thus justifying why they don't have one.
Throwing an obvious one, but the reason why the Shadow Operatives have their final Personas (save for poor Koro-chan) while the Investigation Team are stuck with their initial ones is chalked up to experience. Junpei, Yukari, Ken and Koromaru (funnily enough, all were added to Ultimax) have been fighting since 2009, while Aigis, Mitsuru and Akihiko (the three P3 representatives in vanilla Arena) having more experience before that. Compare that to the Investigation Team, who are still green when matched up in terms of experience.
Further, the Persona 3 cast all upgraded their Personas through unavoidable story events. The Persona 4 cast got their Ultimate Personas through maxing their Social Links, which is technically optional. This game avoids making any Social Links from P4 explicitly canon, so in order to maintain that they can't have their ultimate Personas. Due to them being plot-related, there's not doubt all the P3 Ultimate Personas are canon, so that's why they're here.
Labrys is the 5th Generation Anti-Shadow Suppression Weapon… that means that at some point, four previous generations of robots (with hearts, feelings, etc.) were put through the same kind of hell that she was. That's messed up.