#sick!papyrus

He does not sleep, beloved around or not, he has to be awake to keep watch and protect them, so he's often exhausted, and this lack of sleep may result in him seeing things or becoming paranoid, worsening his protective nature. This can be fixed by begging and pleading with him to just take a quick nap, a short rest, he'll only agree if you sleep with him in his tangle of limbs or maybe even bound in a blanket burrito to keep you from escaping. He'll sleep for a good while to recharge his bones but if you wriggle a tiny bit too much he /will/ wake up.

Id say a good way to distract him for a while is to tell him the house feels dirty or something, he'll go on a cleaning spree, nest must be spotless but you only have about forty-five minutes of freedom before he comes breaking down your door again

Fell sans would probably be a little shit, moreso than usual. Maybe even a little hyperactive, his lovebugg feeding not only off of the bond between he and his beloved but the excess magic that wafts off of him due to stress, meaning he has plenty of energy to invade his bonded's space. Doesn't care if they doesn't want him following them around, not like they can protect themselves, not like they can stop em, he's trying to keep them safe in his own, mean, bullyish way. Even if he has to hide a few bodies or delete a few contacts in your phone he's doing what's best for a weak lil thing like you

Fells general lack of self expression and the distance he keeps from others would also be changed, he'd be ontop of his bonded, constantly, cuddles kisses hugs or he gets an attitude and makes it their problem, missing belongings, grumbling in the corner until he gets what he wants, questionably harmless pranks, the whole mile.

He behaves when given the affection he craves so much tho, perfectly harmless to their beloved when his parasite is well fed and at peace, besides the occasional nip he gives them for the sake of his cuteness aggression, hes no danger to his bonded, just those around them, his distrust of every other living thing in their vicinity could prove an issue. It can come off as jealousy but it's much more akin to food guarding

A good way to distract him for a while would probably be to just hold him until he falls asleep, he'll be out like a light, but when he wakes up and realizes his bonded gone he may have some choice words for them (some whines and questions of if you even love him 😔)

That being said, it makes a pat as obsessive, violent and possessive of whoever they're bonded to, and should they be bonded to an infected skeleton the two (or three in the poly aus) if them will be on top of eachother constantly. They're dependant on eachother for sustenance and are fine living their lives attached at the waists, though they have a tendency to shut down or freakout if their bonded is not around. The relationship is full of the reassurance and affection that both parasite and virus need to survive, but also may result in social isolation or the possible deaths of people around them. They're feeding off of eachother, consistently, to the point where they become more addicted to it than usual and would rather sit in a dark room with eachother than do any thing else. This is also true for parasite infected x parasite infected relationships, say, if you were a sansxsans/papxpap shipper

Now a sibling bond if two infected's is different, and it's likely that one sibling infected the other. Papyri are also alot more susceptible to infection because the parasites that latch onto their souls have more 'bugs' than they're able to give out, so in a house full of papyri they'd all get sick at a much faster rate. (This is because I hc papyrus as just a general power house with more magic than the average monster, so this also translates to his parasite)

Classic sick!Papy CRAVES attention, and will be as loud, flashy and constant as he has to be to get it, he doesn't have to stalk because if he had it his way, he and his bonded would never be apart. He's incredibly generous, and LOVES to give gifts, and is determined to keep his bonded alive and functioning properly. This includes feeding them, keeping them at full hp, enforcing a strict sleep schedule, he's alot more likely to impede on a beloveds autonomy than sick! Sans is. Despite his overbearing nature he can also be a huge pushover, he forces his beloved to eat but will get them only what they want, forces them to sleep but let's them watch a few episodes of their favorite show first, Esspecially if they ask really nicely and offer up some of their delectable affection, how can he say no to that? His bonded earns an obsessive caretaker, all for the low low price of every ounce of their love and attention. (I can also see him using he/they pronouns)

Swap!sick sans is a suave, manipulative mf, who always finds a way or a reason to be in the same room as his beloved, always comes up with a reason for his beloved to need his Assistance. While he comes off as helpful at first, it won't take long for his bonded to realize he's just a control freak, he needs texts every hour on the hour regarding his bonded's condition if he's not in his beloveds field of vision, if he doesn't get them he will show up at his bonded's doorstep to offer them a friendly reminder to keep in touch with him. He wants to know what you ate, when, who you talked to, why, if you still love him, if you think he's as pretty he thinks you are, etctec. Despite his confident persona he needs aLOT of reassurance before a bonded even has a CHANCE of getting him off of their back. If you want him to go away distract him by bathing him in kisses, trying to take care of him (feed him, put him to bed, etc), and running away before he can get wise and attach himself to you like white on rice once again. He does have a tendency to fall asleep on his feet, as his parasite doesn't even allow him to try and sleep unless his beloved is around, which is why he very much insists on having sleep overs, constantly.

They will however hide that their intentions are to feed rather than to love. the host certainly has genuine love and affection in its soul, but the parasite causing said affection to run wild will pretend as if its not manipulating the host solely for the sustenance the magic of a soul bond gives them

There will also be odd nicknames given to the bonded like 'morsel' n 'treat' n stuff related to food, because that's how the parasite sees them, even if the host doesn't realize it

I've also thought about different parasite personalities for different aus!

The best example I have is swap papy, who when infected seems to become incredibly anxious whenever their bonded isn't in their direct line of sight or is talking too nicely with another person, leading to situations of jealousy and the like