He did that a couple of timesPersonally after watching Young Justice, I don’t understand why the Joker never literally became an Agent of Chaos.
Would be a cool way to make Batman the Laughs a part of the DC mainline universe rather than a Bruce Wayne from an alternate timeline. It seems like the natural evolution for the Joker. His obsession with Batman makes him want to BE Batman. Wear the costume like it’s literally his skin.