Oh hey, DP x DC idea
Of which GIW has somehow captured the Joker due to him showing up in their radar. And Danny as Phantom, breaking into GIW thresholds to break out ghosts who were captured and/or experimented by them around Amity Park.
Phantom meeting Joker, ofc.
See, my brain insists that Amity Park is quite isolated in the US due to GIW interferences. So if Amity Park gets news of OMG METROPOLIS IS UNDER ATTACK, or GOTHAM IS HAVING DISASTER, they'd thought of those as fake.
So Phantom has absolutely no clue who Joker even is. He rescued the Very Weird ghost like he does the other ghosts.
And y'all get to continue it 😆
Alright this got me thinking. Realistically Joker probably plans to torture Danny to mentally break him like he did with Tim using electric therapy which... Definitely could get results. (And also be even more messed up if we play with the idea of Danny being hit by electricity forces him to remember his half death)
But even if Danny does somehow become a second Joker Jr and fights the Batfamily... Would he still resist? Like this isn't mind control but if we're going Protection Obsession route or just Danny being a hero at his literal Core, would he subconsciously hold himself back and actively be fighting his obsession which subsequently could be hurting?
If so... OH FUCK that opens a lot of possibilities, especially if it depends on if one of the Bats (most likely Cass or Bruce) noticing Danny struggling to actually hurt them, like he physically can't but he's trying his hardest or else Joker might make him suffer a little longer.
On a side note. I'm just suddenly imagining Joker accidentally dies of Ectoplasm poisoning long before he gets a chance to try anything with Danny because nobody realized until after the fact he wasn't a real ghost, just pinged as semi ghostly on their radar due to the chemicals he's doused himself in.
Just Danny and the ghosts see Joker's corpse and think "aww he's sleepy" and it takes them... Longer than they'd like to admit to realize the clown of Gotham is dead. Maybe it doesn't even register until they see Joker's ghost and reality hits Phantom like a massive tidal wave.
So many options brrrrrrrrrrrr