One of those "Jason becomes friends with Ghost King!Danny in the Zone after he dies" AUs but Jason just. Never leaves. He spends three years just hanging out in the Zone, partially amnesiac and everything. He gets a place in the King's Court (literally just the Official Friend Group of people Danny likes) and fully builds a new life in the Zone.

And then, one day, the Justice League has to travel to the Infinite Realms to meet with the Ghost King (their summoning portals wouldn't work). They travel all the way up to the castle and are told to enter the king's receiving chambers

Imagine their surprise when the king isn't the otherworldly eldrich monster they were expecting but a glowing ghost kid hanging out on a throne messing with his friends

And then the king and the ghosts+court notice the League and settle down, arranging themselves to look more Official(tm). The League approaches, and Superman is laying out the reasons the League wanted to meet with the Ghost King. And Batman, who has been looking around, cataloguing everything in the room, finally gets a good look at one of the Knights of the King's Court

"Jason?"