Dragon Quest IX/WMG

The Hero will turn back into an Angel when s/he dies.
Of old age, accident, whatever. Everyone else reverts when they get killed, afterall.

Jack of Alltrades is a sage.
Think about it.

Jack is a holy man with the ability to change a person's vocation. The ability to change a character's vocation is a sage ability called "Voice of Vocation". The reason he's the only one who can do this is because the vocation itself is so rare (gotta finds that sentient book, remember?)

Coffinwell tells the origin story of Hina Kagiyama.
Catarrhina looks strikingly like Hina, and her hometown suffers under a curse. Her only thought is to help those around her, particularly her beloved Phlegming. After everything in Coffinwell is resolved, Catarrhina eventually finds herself in Gensokyo, reborn as a yakubyougami -- but rather than spread misfortune, she uses her powers to absorb it instead.
 * The fact that she can come back at will from where souls go to check on Dr. Phlegming from time to time definitely suggests she gained power and authority in death that most souls do not receive. (Even Nodolph said that nobody ever comes back.)

Early in the story, the hero tells his human party members everything.
At the very least, before boarding the Starlight Express the first time. They, being your standard Adventurer Player Mooks, thought this was awesome.

The human party members are Dead to Begin With.
But aren't non-corporeal ghosts like the ones from this world. Before their final destination, their souls dropped by the Inn Between the Worlds are paired up with the Almost Human hero. The Hero can summon them at will like Phantom Brave or Valkyrie Profile but they have no presence and are invisible when the hero talks to other people. In fact, this is why the hero never relies on them to  despite Fridge Logic indicating that they, as humans, wouldn't have the same limitations. They're beholden to him/her.
 * did not end this ability, as their presence is part of his pure wish. He is still able to see dead people. They may have faded too had he not
 * But if your hero dies, NPCs will react to the others (The most apparent is the baths in Gleeba, particularly with an opposite sex 2nd and you are told to leave them behind once in the story (which you shouldn't need to do if only you can see them).

Conversely, the human party members are Persona-esque figments of the main character's imagination.

 * See the above reasoning.

Celestra is the Goddess from other Dragon Quest games.
She took over for Zenus, but the Church itself is a Saintly Church, so she kept it the same besides the new symbol.
 * In fact, given how it remained benevolent even when Zenus was in charge, and he apparently hated humans; she was probably the one who created it using Zenus's name.
 * Celestra's effigy being behind the nun at Slurry Quay, and the Goddess statue in supports this. There's also a Goddess Shield in the quest 182: Immaculate Conception. The quest giver recognizes the picture of the Goddess, then seems confused and claims it looks like his ex-wife. This is the Fisher Kingdom effect slowly taking effect as she's taking over.
 * Interestingly, characters from previous games who worshipped the Goddess who show up in the Quester's Rest will refer to the Almighty instead.

There is no Annabella in quests 56 and 57.
So, on an island surrounded by shoals, where no one can get to; there's two houses. Both have a man who loved a woman Annabelle, both bought her the same amulet, and then she died 3 days later. Both accuse the other of stealing it, and both lost it to monsters that you can retrieve it from and give it to the other. Indefinitely. Both have a "large diary", but you can only read 3 days worth, the rest is unreadable. They talk about how tired they are.
 * Man, that Annabelle must have been some player or something right?
 * Wait... there's a monster that sometimes appears on the island. A Cannibelle. ....ohhhh dang.

The inhabitants of Porth Llaffan are descended from Celestians.
How else can they see and hear when he appears as a ghost during the cutscene after the boss of Twyll Cave? It had been established that only Celestians can see ghosts...and yet, everyone from Jona to the mayor is having a chat with this particular ghost. Alternate explanation: a fygg did it.

The Player Mooks are, in story, the same thing as multiplayer helpers
That is to say, alternate universe versions of the protagonist. Like the protagonist, they're silent protagonists, which is why none of them ever check notes on how far they are in their own respective journey. This is why the rest of them suffer the same Celestrian problems as the protagonist.

Sterling is really Styrmling, the third brother of Greygnarl and Barbarus.
Mentioned only by. He separated his power (or else Zenus did) into the Celestial Train.

All of the Multiple Choice Past options are true for

 * When Celestra became a World Tree to prove humanity's goodness, Zenus created another daughter,  to prove their villainy. To counter Celestra's choice, this second daughter was given two bodies, one World Tree on Luvi Island, which ironically prevented souls from being able to Ascend to A Higher Plane of Existence by resurrecting them in this world and one   The plan went Horribly Right when   denounced the Almighty, lead the Gitt Empire to Take Over the World, and burned her World Tree to the ground. However, she died when a retainer stabbed her.

This was not the end. was reborn as a child, and her World Tree became a ghost World Tree. However, she died as a child; and her soul wasn't developed enough to go to heaven or hell;  The Almighty, deciding it was best to keep her soul under close watch, appointed her to

Zenus wanted to destroy humanity because of the Gittish Empire

 * Think about it. Zenus argued that humanity was too inherently sinful and needed to be "restarted", so to speak. The Empire is shown to have been 99.9% made up of Complete Monsters who considered crossing the Moral Event Horizon a daily past time. Plus, he was probably very pissed off over
 * That last bit isn't possible. The Celestrians, Corvus included, didn't exist until after Celestria stopped Zenus from destroying humanity, since he created them in order to free Celestria.
 * And by extension the rest of it isn't feasible either. The atrocities committed by the Gittish Empire included capturing Corvus, which occurred hundreds or thousands of years after the creation of the Celestrians - as is said in-game, the Celestrians have existed for millenia, while Corvus disappeared 300 years ago.

Patty can use the Rapportal, or a roughly equivalent power.
This is how she can instantly call up somebody who fits your hero's exact description of who and what they're looking for. She just does a quick search and pulls them through.
 * Then why do they stick around if you die?

The Player Mooks are slaves.
Notice how they all wear the same beige clothes when first created that the hero in DQV wears during his time as a slave.

The main character's canonical name is Leo

 * This is what I named him, but I didn't realize the Fridge Brilliance behind it until later. First of all, every Celestrian that has a name is named after a constellation representing a bird who's personality is similar to theirs. Leo is a constellation that represents a lion, which is decidedly un-bird like, foreshadowing his loss of wings. Also, the star sign Leo is probably the one most fitting of a hero, as they tend to be brave and have a strong sense of justice. Since this game is big on Meaningful Names, I reckon this is the most fitting title for the male hero.
 * Thank you. This is now Fanon for me.

The main character's canonical name is Cygnus/Lyra

 * Both are birds, Lyra orignally being a vulture, and both are apart of the Summer Triangle...with AQUILA! That was visible during the English release! Coincidence? I think NOT!
 * Naw, I like Leo better. Mainly because there's more symbolism there.
 * Isn't Cygnus one of the two Guardians of Stornway?

The main character's canon name is Ursa/Callisto if female.

 * Taking a page from the person for the Leo theory, Ursa makes sense as the female name. Why? For one thing, it is also a constellation, or rather, a set of them: Ursa Major and Ursa Minor. Both of those are obviously not birds, like Leo, showing how out of place the hero would be (you don't hide a bear in a flock of birds). Bears are also powerful creatures (especially when their young are threatened) and have been symbols of power and strength, especially for early Germanic tribes where they were totemic animals and for many other cultures that practiced bear worship. They are fierce, yet motherly, and don't back down easily. Bears as a species were believed to all be female by the Greeks, making it perfect for a girl's name.
 * And why Callisto? Callisto isn't a constellation, but according to Greek myth, she was a nymph of Artemis turned into a bear by the goddess Hera thanks to Zeus' shenanigans, then placed in the heavens to become...(wait for it) the Ursa Major constellation.
 * Hello, this is the troper who came up with the Leo theory. You sir madam, have just made my day for mentioning me. Please accept this TV Tropes Made of Win Archive.
 * Oh, thank you! I'm a girl though~
 * There, I fixed it :-D

The hero's full name is...

 * Leonardo Cygnus (Male)
 * Callisto Lyra (Female)
 * Now who was it that said you can't combine the theories of two different WMG's?
 * Callisto Lyra does roll off the tongue rather nicely.

The hero's REAL name is (sic) By-my-name

 * On the high plateau on Newid Island, there's a kid who's supposedly lived with the giants up there all his life. When he sees you, he calls you Mr. Tiny. The hero supposedly says something along the lines of "Call me by my name" and the kid says something along the lines of "Okay, Mr. By-my-name! This may seem irrelevant, but this is the ONLY time anybody actually names you anything. Hey, it's not the craziest WMG I'VE ever seen...
 * Hey, kinda like how everybody called the Hero from Dragon Quest VIII "Guv'" and people thought THAT was his name, eh?

More people will try and guess the canonical name of the Hero.

 * Go on, take a guess at what his/her name is. You know you want to.

Unknown to the Main Character, Corvus is his/her older brother

 * Seeing that there's endless possibilities for the main character's past. It could be possible that he or she was born after Corvus disappeared and his/her parents or guardians never told him/her about him because it was forbidden to so.
 * This is technically true, but it wouldn't be a secret to anyone. Celestrians don't have parents in the same way humans do. They were all created by Zenus, so they're all brothers and sisters. ( and call each other Brother and Sister specifically because they're "twins," created at exactly the same time.)

PC/Erinn is a foil to Corvus/Serena

 * Serena and Erinn both look after their guardians once they take them in. And PC/Corvus help them out, or at least try to. Puts a different spin on PC/Erinn's relationship, and the Les Yay implications if female.

The Hero Spear used to belong to Erdrick

 * Sure, it doesn't require Orichalcum to make. Sure, you can get multiples of it. However, the Hero Spear has the exact same design on it as the rest of Erdrick's Gear, so much that if you put them all on the spear doesn't look out of place at all. Hmm...
 * Notable also that it's in the style of the 'Rusty' (i.e Erdrick) equipment, yet when the ghost in Stornway castle gives you a Hero Spear as a quest reward, it's in perfect condition. He's also old enough to be familiar with the alchemist buried in Brigadoom.

Metal Slimes are made of Orichalcum

 * First of all, the Metal Slime gear mentions that it's "made out of Metal Slimes". In order to upgrade the stuff, you need Oricalchum. Put two and two together...
 * My my, that's just crazy enough to be true!