10 Times Batman And The Joker Saved Each Other
2. Joker Stops Batman From Breaking His Code - The War Of Jokes And Riddles
Tom King covered a hell of a lot of ground over the course of his extended run with the Batman character. One of his major events was a large scale war between classic Gotham villains the Joker and the Riddler, told as a flashback and set during Bruce Wayne's second year as the Batman.
With the Joker on a murderous rampage trying to find something to make himself laugh, and the Riddler recently broken out of prison and looking to remove Bats from the picture, Edward Nygma approaches the Clown Prince of Crime with an offer to help him off their mutual enemy. The Jester of Genocide refuses, attempting to instead kill the Master of Riddles, igniting a city-wide war. All manner of chaos ensues, as you can imagine, before Batman has the Riddler completely at his mercy, and is about to strike the finishing blow.
The Joker, of all people, stops this from happening, and the irony of it being him who prevents Bats from breaking his moral code is enough to bring the gift of laughter back to the maniacal clown.