The moments when Tikki or Plagg couldn't transform with their holders were a rare occurrence and even then, they usually hated it. Most of the time that meant that the Kwami, themself, had gotten sick, and yet sometimes that meant the holder had gotten sick.
Rarely, did they catch stolen moments together right on time when they were sick, and yet here they were, sharing a small spot beneath a blanket, huddling close as Rena Rouge and Carapace went to save the day while Adrien and Marinette both lay sick, huddled close, 'because it was easier to watch two different sick people that way.'
Alya and Nino had probably been scheming with another attempt of getting their best buds to be a couple, and while Adrien and Marinette were cute in a way, huddled close, too tired and too sick to notice just who they were cuddling in Nino and Adrien's hotel room on this field trip, Plagg and Tikki didn't have that oblivious air. They knew who they were cuddling, and they weren't afraid to cuddle close.
Over the years that they've had together, the two Kwami became the best of friends and something a bit more than friends. They didn't mind cuddling or huddling close, they didn't mind if they accidentally eskimo kissed each other or if they gave each other a light kiss, just to pretend that they were human and were allowed the luxury of not dealing with losing chosen over and over again before they had to move on since they could not easily be lost.
Immortality had its downfalls, but it also had its plus sides. It made them so very aware of just who the other was in a way that humans could rarely achieve, and now, it made them aware of just how to tuck their little bodies in and cuddle close for maximum comfort and hopefully to break these fevers. Master Fu wasn't on this trip to give them a quick fix, but they also knew that it wasn't a serious sickness.
They'd probably came down with whatever their chosens had gotten, and Tikki and Plagg, right now, were too warm and snuggly to coo over how 'precious' their chosen looked unlike the two that were supposed to be watching them and yet couldn't at the moment.
Tikki nestled her head right beneath Plagg's chin and pressed closer, half curling her feet over his lazily, and she relaxed. Every breath brought the scent of Plagg to her nose, and yet she didn't mind and while Camembert could often make her not very hungry, she had no hunger to lose, and she'd long since adjusted to his strange tastes until he found something else that Tikki likely wouldn't share the same interest in.
Either way, nothing else mattered in this moment as four minds were lost in a fever induced haze, not as two Kwamis found that the best, cuddliest warmth were each other, just glad to be next to each other after so long apart.