I mean, they do a Joker origin story like every batman reboot.
You mean in the adaptations? The first Burtman gave him an origin story, and I suppose the Telltale series is currently in the middle of one, but that's all I can think of. Adaptations like
The Dark Knight, the DCAU, Bamham, and Batman '66 all wisely kept his origin ambiguous. Even
Gotham is currently staying vague about what connection, if any, Jerome has with the future Joker, and this from the show that delivers (what it imagines to be) fanservice with all the subtlety of an elephant crashing into a grand piano. (Incidentally, the best episode involving Jerome, and one of
Gotham's strongest overall, was when he squared off against young Bruce Wayne in a quasi-adaptation of
The Killing Joke. It's almost as if the Joker is at his best when he's fighting Batman!)
And Harley Quinn was in it well after the Joker was established as a psycho. That's basically two origin stories in one movie and let's just... no.
I'm not sure what this means. Harley was in what?