So this is incredibly random but there was talk in the Discord of a Dragonblade AU where Jester inexplicably comes back to life, but it's gradually revealed that it's not actually him, it's another spirit possessing his body and pretending to be him.
My first thought? The Evil Ghost! John D'ark au.
In this au, D'ark's ghost has either been watching Jester + the castle residents for some time, or has been secretly somehow communicating with them. My mind immediately goes to Jester-he wrote a song about the old knight, so John would latch onto him and subliminally influence him in his life. Then, after Jester kicks the bucket in DB, John takes full control of his corpse. He's been around Jester long enough to decently imitate a good amount of his mannerisms-but there's definitely enough off about the way he begins acting for people to become uncomfortable. Most dismiss it as the trauma of his "horrifying near death experience", and that settles things for a while. But those closest to him, Jane and Co., just know that as happy as Jester suddenly seems to be after recovering, something is still seriously wrong. I feel like Jane in particular would be attuned to these changes-not only were she and Jester best friends, but, as Jane's grandfather, John is very interested in her and her life. How weird would it be if your bff's interest in your life activities suddenly changed from a manner that was platonic to paternal, grandfatherly?
(I have an idea-in this au, Jester breaking into Jane's room and crying over her stuff is the result of his possession. Either Jester and John fighting for control, or John becoming emotionally overwhelmed at his own circumstances. And as I've mentioned in Evil! John D'ark au concepts before, I have a theory that Evil! John would disapprove of women being knights as he came from an older generation. So discovering his granddaughter is a knight-or at least training to be one, under the tutelage of his former best friend-would make him...feel things, for better or worse.)
Speaking of Theodore, he would be the most disturbed of all. Sure, he's seen people and their demeanors change after severe trauma and/or near-death experiences, he's a knight, it's part of the territory. But this? This is unlike anything he's ever seen before. He can't pinpoint what is wrong with Jester, only that something is. And he shouldn't have recovered this quickly to begin with...
But he shoves the concerns out of his mind. All that truly matters is that Jester is alive and seems to be mostly happy, that's really nothing to worry about...
But then one day when the two are somehow alone together, an old nickname that only John D'ark ever used for him slips out of Jester's smiling mouth.