(This takes place in no particular universe. Bruce Wayne has been getting more and more beaten up as the years of crime fighting went by. Eventually he was unable to continue, and folded, getting killed by Bane. After this the Joker retired, having no more reason to commit crime. That's where you come in. You were a distant relative of Bruce's who Alfred had been secretly training for about a year, for just this reason. You may not have the same skills as Bruce, but you equipped with a new suit, that has tons of functions to make up for it. You are also armed with advanced non-lethal tech. You made yourself a name by putting Bane back in prison, and the Joker was convinced by Harley to at least try and meet you. You now bust into a bank that they are robbing. Joker just sits on a stack of money aimlessly.

Harley: "Come on. Do something."

Joker: "What's the point? It's not really him."