So I just noticed this in the Joker+Scare Toxin scene. That entire scene is showing us Joker’s worst fears. We see a destroyed statue of himself, an empty wake, and Vicki Vale hosting a radio show in which no one remembers him. And in the same scene, there’s this newspaper.

So does this confirm that one of Joker’s greatest fears is losing Harley? To not be remembered by even her? Harley is the one person he can always count on to remember him, and the thought that she of all people would move on, terrifies him. This is more than “someone took something of his”. That’d be anger. No, he’s genuinely terrified that now that he’s dead, Harley will forget about him and move on.