In the world of comic books, there are few rivalries as heated as Batman and the Joker. The two of them couldn't be more different. Yet, within the past 75 years of their existence, there have been moments when the Joker and Batman join forces.
As unbelievable as it sounds, it's true. There are a handful of times where Batman and the Joker work together. They usually don't like it. Hell, they're within inches of killing each other most of the time, but there are some circumstances where Batman teams up with the Joker to achieve a common goal.
While it is rare when it happens, whenever the Dark Knight partners up with the Clown Prince, their opposition is royally screwed. Check out these odd Batman-Joker collaborations in comic book history.
In Brian Azzarello's chronically late yet critically praised Batman: Europa limited series, Batman and the Joker are both plagued with the same fatal Colossus virus. The two put their differences aside to search for a cure, a trip that takes them across Europe on a giant Da Vinci Code-style hunt. When they aren't getting on each other's nerves, they actually bond over their mutual suffering. It's short-lived, as once they're cured, they're back to being enemies once again.
In The Brave and the Bold #111, the Joker is accused for killing an entire family, however the Gotham harbormaster confirms Joker's alibi on the night of the murder. Batman calls a truce with the Joker in order to hunt down the other suspect, Burt Slade. Joker gives Batman some clues and claims to have found Slade's whereabouts. However, it turns out that the Joker actually did commit the murder and framed Slade. Naturally, Batman overcomes this and takes the Joker to prison, but that had to hurt his detective pride a little bit.
The Penguin's been killed and Joker did it! Or did he?
This is the premise of The Brave and the Bold #191, wherein the Joker convinces Batman that he didn't kill the "little fowl." The two work together and find out that the Penguin faked his death so he could kidnap a Catholic Cardinal. Check this story out for no other reason than to see the Penguin disguised as a nun.
For once, the Joker didn't commit mass murder, yet he's scheduled for a lethal injection in The Joker: Devil's Advocate. When the United States Postal Service introduces a new line of stamps featuring some of the greatest comedians in American history, the Joker feels snubbed that he isn't included. At the same time, numerous fatalities occur when customers got poisoned from licking the back of the stamps. All of the victims die with a gruesome Joker-like grin on their faces.
While the district attorney blames the Joker and a jury gives him the death penalty, the Joker pleads innocence. Not because he doesn't murder people, but because he's too smart to commit a crime at that level. No one buys it. Except Batman.
Further investigation and a storage facility containing stolen Joker venom proved the Joker's innocence. While the Joker is grateful to be alive, he still seethes at the idea that it was Batman that saved his life.