Why did the Joker cross the street?
I do not know.
Maybe there was a big pile of shit on his side?
Or maybe he wanted to buy cigarettes and saw the store on the other side?
Does Joker smoke?
I don't think he thought he was going to die of cancer anyway.
Maybe he saw Batman and wanted to high-five him and say:
Hey Batman! Since I have terminal cancer, I wanted to say, I love you man. You complete me.