Yes, there are quite a few. Some explore a different side of the Joker where he has a moment of redemption and saves Batman. It often plays with the complex relationship between them and the idea that even the 'villain' can do a heroic act.
One common theme is redemption. It shows that even a character as chaotic as the Joker can have a moment of good. Another theme is the blurred line between hero and villain. It makes readers question if the Joker is really a villain in that moment.
Their relationship would become more complex. Batman might start to see the Joker in a different light, perhaps as a victim of his own madness rather than just a pure villain. The Joker, on the other hand, might be confused by Batman's act of saving him and could develop a strange respect for Batman, or he might try to use it to his advantage in some new, devious plan.
At first, Batman would be shocked and a bit confused. But quickly, his detective instincts would kick in. He would view the deaged Joker as a new and unexpected threat. He'd start gathering information about how the deaging occurred, in case it was part of a larger, more sinister plan. Batman would also be very careful not to underestimate the deaged Joker. He might try to isolate the Joker in a secure location to prevent him from causing chaos in Gotham. And he'd be constantly on the lookout for any signs of the Joker's old, devious self emerging from this new, younger form.
It can completely change it. Usually, there's this cat - and - mouse game between them. But when Batman hurts the Joker in fanfiction, it might make the Joker more vengeful. He could become even more obsessed with getting back at Batman.
Some writers explore their relationship through a cat - and - mouse game. Batman is always chasing the Joker, and the Joker enjoys taunting Batman. It's like a never - ending dance. For example, the Joker might leave clues for Batman just to see if he can solve them, and Batman is always one step behind but determined to catch the Joker.
One idea could be that the Joker kidnaps Batman to force him into a series of cruel 'games'. Maybe he wants Batman to choose between saving his closest allies or innocent civilians, testing his moral limits.
A really interesting fanfiction is 'Joker's Gambit'. In this one, the Joker sets up an elaborate scheme that not only challenges Batman physically but also mentally. It's full of unexpected twists and turns that keep you on the edge of your seat. The author does a wonderful job of portraying the cat - and - mouse dynamic between the two iconic characters.
This is a rather complex question. Batman is clearly intelligent. He has been trained in multiple disciplines, from martial arts to forensics. He uses his intellect to solve crimes and protect Gotham. The Joker, though, is a different kind of intelligent. He has an almost insane creativity when it comes to devising his evil plans. He can read people very well and use their weaknesses against them. He doesn't follow the normal rules of society or logic, which in some ways gives him an edge. For example, Batman often has to rely on his moral code and the law, while the Joker has no such constraints. So, it's not really possible to simply say one is more intelligent than the other.