Nonhuman Characters
"I'm sorry, Teddie... Only people have human rights."
- --Naoto Shirogane, Persona 4 Golden
On the Velvet Room MUSH, Shadows may only manifest within supernatural spaces, period, end of story. That is the rule! And yet, modern Persona games have a tradition of characters like Ryoji Mochizuki from Persona 3, Teddie from Persona 4, and Morgana from Persona 5 that can exist in the material world.
What gives? Doesn't that seem like a contradiction of the rules?
This file is to establish guidelines for players who want to play a character who is a Shadow, or perhaps even a Demon, or some other supernatural-origin character occupying similar narrative space. Beware spoilers for all of the above games and also Persona 5 Tactica.

The Rule
If you want to play a character long-term on the Velvet Room MUSH, then the character must be able to exist in the real world. There are just too many scenes and roleplay opportunities that will exclude the character otherwise.
So the rule is: if the character within approximately six months of application can't participate in a social scene at the Big Bang Burger, you can't apply for them! Obvious supernatural features are out. Technological features should be hidden but are not disallowed in the same way.
(We should stress: the timeline is negotiable; we know things happen. We don't want players to feel so crunched that it must be done by that time. However, a plan for that character to have a Persona and be able to exist in the material world is not. If you want to app a character like this and don't want them to already have a Persona, you MUST include a plan on how to make that happen in your app. More further below on why this is important.)
Now, that doesn't mean you actually have to do that specific social. It just means if you'd go, 'My character literally is incapable of doing that social scene and I don't want to do an arc to change that,' this character isn't appropriate for application.
Morgana can be in Ren's bag; Teddie can be in his mascot costume or human form; Jerri from Persona 5 Tactica: Repaint Your Heart, who's been expanded into this group on Velvet Room MUSH, can be complaining on a PC's shoulder.
So long as that's the only limiting factor, then this is a character that can be played!
Let's Clarify!
So how do we get there? It's simple: the reason that a supernatural being can exist in the material world is because they have awakened to a Persona. A Persona is a stabilizing force that allows them to contravene the rules regarding supernatural spaces.
Teddie only enters the real world after awakening to a Persona. Morgana begins with a Persona and can enter right away. A theoretical nonhuman character such as a Velvet Room attendant would need some arc to leave the Velvet Room, but might have one or more Personas. These characters by their very nature would be subject to intense limitations, including a 'minimal interference' clause, but they are possible.
So then what about Ryoji, you might ask? He's a Shadow. However, the game also makes it clear that he is Thanatos. He is a Persona himself. Here, we're going to make the rules for such characters very simple.
You can't actually be a Persona. Your character must be a Shadow or a Demon with a Persona. Ryoji is thus the Death Arcana Shadow with the Persona Thanatos. That stabilizes him to exist in the real world.
After the end of December in Persona 3, Ryoji would no longer be playable in the material world, as he makes his transformation into the Nyx Avatar. The timing of this would be up to the player and their cast. They're on the end run of their arc, and could thus be played until the final battle, but could no longer exist in the material world for social scenes.
Demons
Now let's talk about the Jerri example. Jerri is a Demon in the service of the Stagnation. She exists wholly within the cognitive worlds that she invades and can give strange powers to the people she preys on.
She does not have a Persona; she's a pink cockatoo Demon, and in the final battle of Persona 5 Tactica: Repaint Your Heart, she transforms into an odd, enormous cephalophore form that's similar to her boss.
So how can Jerri be a played character?
Simple: she can be if she's given a Persona and can exist in the material world. So long as she has that, she can meet the bar of 'can social at the Big Bang Burger.'
For characters such as this, we're instituting another rule, which is similar to Ryoji. Once they make that transformation into something greater, the Final Boss Form so to speak, they lose their ability to exist in the real world. The end of their arc begins when they transition into this form, but they remain playable until that final confrontation and the aftermath.
However, we're instituting another rule specifically for Demons: Demons that exist with a Persona in the material world must be antagonists long-term.
While Demons can cooperate with humans under certain circumstances, a Demon with a Persona is always the result of a malevolent Guide facilitating it. They are servants, sometimes direct servants. They can make relationships and bonds with humans, certainly. But becoming a protagonist results directly in the consequences of a malevolent Guide punishing them, something that would end their arc.
The Pathophysiology of a What Now!?
So you now have a Shadow or a Demon in the real world with a Persona. How do normal people regard it? If the Shadow is very human, then exactly the same.
If they take the shape of an animal, then unawakened individuals who have never been to the Metaverse will hear them as animals. Until they've interacted with them in a supernatural space, their cognition will not change, but once they do, they will be able to understand their speech.
Note: like regular people, they can't summon their Personas in normal spaces. Jerri is effectively a bird and Morgana is effectively a cat, physically.
So what happens if you take them to a doctor or a vet? Will they realize something is wrong?
Yes and no. Upon physical exam, they will be exactly the same as people or animals. Every method of physical assessment will just show they're people or animals.
Well, what if you do blood tests or imaging?
The blood tests won't run. The imaging will be entirely opaque. Technology that assesses the parts of animals or people scientifically just won't work. Normal doctors will be baffled, but cognition usually asserts itself to let them explain it away as just a weird malfunction and not consider it an actual medical mystery.
It must be stressed, however, that while Demons and Shadows cannot truly be harmed by the unawakened within the supernatural world, once they gain a Persona and choose to enter the material world, that no longer applies.
A man's kick will hurt Morgana gravely. A person stabbing a Demon will do the same. However, so long as they are not killed, Shadows and Demons heal at a much faster rate than people and animals.
The same goes for illnesses. Shadows and Demons can get ill! Or even be poisoned! But so long as they don't perish, they'll generally recover much faster. That's good for them, because mundane medical intervention is possible, but only to a certain degree.
Bodily processes are also largely the same for the form they take: they must eat, drink, breathe and 'do their business.'
Note too: for animal forms in particular, they are not confined by the same dietary restrictions as those animals. A dog Shadow eating chocolate will not suffer potentially awful consequences. However, their senses will function cognitively the same as the animal they're taking the shape of. Morgana, for example, may not be able to tolerate spicy, extremely hot, or extremely cold foods even if he can technically digest them.
Koromaru, however, is not subject to these rules and would be in mortal danger if he ate chocolate, same as any other dog. Sorry, Koromaru, you are in fact a real boy!
Anti-Shadow Suppression Weapons and Robots
Anti-Shadow Suppression Weapons and other robots who otherwise have a Shadow or Demon within them are largely special cases among these special cases. By their nature, they can enter the material world right away and exist there without a Persona. Those like Aigis can also be modified for social scenes to pass as human at a glance. There's more wiggle room for technological advancement than there is for supernatural flesh.
Nevertheless, in the long term, we require that each of these character types achieve a Persona.
Anti-Shadow Suppression Weapons in particular are restricted at the start of the MUSH, but once they become available for application, they cannot be applied to remain Unawakened in the long term. They must develop a Persona.
For these characters in particular, their hardware can break and must be repaired! Persona healing spells can assist with some damage in supernatural spaces, but other types require far more serious intervention.
These characters also require constant recharging, typically in the form of charging stations while they're 'asleep.'
Characters like this may eventually defy the technological rules in some small way. For example, when Aigis' neurologic circuits are fried at the end of The Answer/Episode Aigis, she still exists, because she's a being beyond the technology of her frame and chassis.
Even then, she still requires recharging!
Note: Even though they are robots, they must still remain of human shape and form.
The Kirijo Group notes that attempting to make an Anti-Shadow Suppression Weapon a 'tank' for example would be so incongruent with a psyche, that the body dysmorphia would cause it to not develop properly, and eventually fracture apart. This includes Robots that do not utilize a Plume of Dusk as a basis for their psyche.