i've been thinking about the main six monsters and their dominant soul virtues ('cause i like monsters with soul-coloured blushes and ectogenitals) and so far, based on what i know of from the canon and trying to avoid repeats, i'm relatively sure of: toriel - integrity (blue) papyrus - bravery (orange) sans - patience (light blue) undyne - kindness (green) i'm not as sure about alphys and asgore, which should get perseverance (purple) and which should get justice (yellow). alphys is associated with the yellow soul power but i'm not sure if she fits justice in any way other than that. and i can see asgore as perseverance under my "perseverance stays within the rules even when the solution isn't within them, determination breaks the rules" theory, but i'm not entirely sure about it fitting him. six human souls, six lost souls, so yeah...
i'm attached to the orange papyrus headcanon, and i read a good tumblr post about how kindness actually does fit undyne. how kindness is what motivates her to fight for the underground and befriend papyrus. it also touched on how bravery fits papyrus, how it is really brave of him to stick to his ideals no matter what regardless of how likely it is to get him killed. so yeah, that's where i got that from. before reading that post, i'd never really thought about how kindness could fit undyne.
Integrity also fits Papyrus! anyway thinking of my old demon!Chara AU like, AU where Chara became An Actual Literal Demon after dying, instead of becoming one half of Chasriel demons in this AU come in two general types: totally amoral or blue-and-orange morality demons-born-demons, generally either from nowhere or from two demons deciding that having a kid would increase chaos/suffering/whatever in the world more than it'd cause competition, and demons-born-other, from people, animals, etc dying and then becoming demons. Demons can't outright break deals, if they make them, but they can abuse semantics and the like. Chara's fond of kids but doesn't like humanity as a whole-basically they're a misanthrope who believes that kids are OK but mostly taught by adults to all be jerks. This is partially because of their experience on the Surface while alive, and partially because they keep running into cults. Their main contact with humanity is: various people summoning them for the Vine, abused kids summoning them to get out of the abusive situation, cultists, and one small set of social workers who deal with the kids Chara rescues. One day a cult trying to summon some really nasty demon who likes to eat live human sacrifices mucks up really badly and summons Chara by mistake. They tried to go through with the original deal and Chara screwed them over and that's how Chara ended up raising a kid. The kid is Frisk. Chara accidentally teaches them to carry a swear jar with them at all times and ambush swearing people with it.
the wording of the deal was probably something along the lines of "if you give us [thing] then this kid is yours" and chara was like "okay" and screwed them over and adopted frisk
on a different note consider: asriel's resurrection spell thing only not getting chara because it didn't have enough power to rez them and move the dirt out of the way by the time it reached them so it just...sat there a while later frisk goes there and flowey starts teaching them How To Really High Energy Magic and then suddenly there is a hole and a very confused chara or, alternatively: it's only by the time frisk starts teaching undyne How To Really High Energy Magic there (because they've decided that obviously that's where lessons are), and then suddenly hole
They have a grand time dancing with Mettaton under the discoball, I think it's plausible. Spoiler: spoilers about disco i've had this image saved in my folder since january 2016 i can't believe i finally had a relevant time to share it
au where the Underground shattered into a bunch of AU undergrounds and Frisk, postgame, goes to a different Underground to free them, too resulting in there being two different versions of all the non-Frisk major characters on the surface then Frisk does it again and again and again their head gets very crowded, they end up with like 10 Charas and another Frisk in there, all trying to narrate
about something totally random, like pie, or cats, or star wars frisk is like "guys. guys. i am trying to focus on not dying here." every so often a chara falls asleep and it becomes arguing+snoring
one of them sleeptalks all the others start talking about the total nonsense they're spouting an asriel ends up in frisk's head when they're freeing one of the undergrounds he is very confused because by this point the charas are arguing over whether asriel's palm beans are cuter than his toe beans
it is very crowded one chara figures out how to mindscape and they're all like. "I"M GONNA CLIMB ON EVERYTHING AND CUDDLE YOU ALL" because they're a bunch of touch-starved sense-deprived spirits frisk goes to sleep and wakes up in a Chara Party every time they visit a timeline they get 1 more chara eventually they meet an adult chara like in scramble saga, with the telepathic link spell they are like "i'll start up a link to guide you-...why are there so many child mes in your head and why are they having a party in a mindscape with memory pie made of your magic? there's hardly room for you in here!" one chara is trying to flirt with the asriel. another one is very tired and mistakes the older chara for frisk and tries to flirt...really badly...and then falls asleep standing up. big chara is like..."wat r u doing"
eventually toriel stops them and they're like "does anyone know a way to make 20 spirits tangible" and everyone else is like. what were you doing. why are you so haunted. luckily there's like 22 alphyses who all try to collaborate to make robot bodies for all the charas and the frisk and asriel that need them by that point the Chara Party has turned into a Chara Sleep Pile
one of them went around making things and setting them on fire frisk is like "guys, this is in my head. please stop with the fire. have some more pie instead." charas cycle out between narrating for frisk and the chara party
there is a quiet dark room for charas that had been stuck in their body after it got buried there are many, many blankets one chara spends an entire runthrough just...sitting there the next chara comes in there and there's a chara there who made a blanket nest and just...fell asleep and slept for the entire run then there is a succession of increasingly colourful and loud rooms frisk is like "why are my magic reserves not growing very fast anymore" "oh yeah" "the party in my soul" "attended entirely by spirits, which eat magic" "i am going to show up and make sure they didn't break anything and also maybe redecorate"
spoiler: nothing was broken frisk gets them a chandelier five of them decide to narrate because frisk tells them tales of what happened last run and they're like...i wanted to see that frisk gives them a giant wall TV thing letting them see (and remembers to make a way to turn it off if there's something they don't want the spirits to see/hear) every so often a spirit leaves the Party Mindscape to bodyshare with Frisk one time they all decided to start bodysharing at once and it was a mess a hilarious mess but still a mess (frisk was fine, they got nothing worse than a few bruises) ETA: the TV thing also lets them commentate
some of them probably don't want to leave the inside of frisk's head frisk might then just...keep doing the thing, but with toriel and possible some other adults helping the inside of frisk's head gets a permanent Chara Party