@Cadman from what I can deduce Joker and Batman from the Phoenix movies went back in time to the night Bruce’s parents died, in that movie their death happened at the same time as a joker riot. I think joker just went back to plant the seed that he’s not that bad of a guy. No idea why Batman made out with joker in front of his past self. I think the Batman and joker of the this universe share a Batman/catwoman like relationship since he’s still knocks his lights out to take him back.