Honestly, I've always found the 'shipping' side of BatJokes a bit distracting from what really hooks me—it’s the absolute psychological warfare. Batman’s entire code is about control, restraint, the line he won’t cross. Joker exists to prove that line is imaginary, that Batman’s power is just a costume over the same chaos. In a lot of fics, that gets turned into a horrifying intimacy.
Joker doesn’t want to kill Batman; he wants to own him, to be the one person Batman can’t predict or ignore. The power dynamic flips constantly—Batman has the physical upper hand, but Joker dictates the emotional and psychological battlefield. I read one fic where Joker systematically destroyed every safe house, not to hurt Batman, but to force him to only have one place left to go: Arkham, to Joker’s cell. That’s not romance; that’s a hostile takeover of a person’s soul. The 'relationship' is a cage they build together.
The best ones make you question who really has the power. Is it the one in chains, or the one who can’t stop visiting the cell? It’s less about who’s on top and more about who’s trapped.