#sick!sans

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 😔)