The Joker remains one of the scariest forces in the DC universe, but Batman’s strict moral code keeps him from ending this clown prince of crime once and for all. So, while we know why Batman doesn’t kill the Joker when given the chance, it’s not always clear why the Joker hasn’t simply killed Batman when given the opportunity over the years. And the answer is as simple as it is shocking: it’s because the Joker is in love with Batman.
The theory that Joker doesn’t kill Batman out of love is supported by actual dialogue from the comics.
In case you think we’re really reaching here, this is something that Joker has actually said to Batman on a number of occasions, and there are even more instances where it is merely heavily implied. Perhaps the most obvious example comes from Scott Snyder’s excellent “Death of the Family” storyline, in which Joker decides to torment Batman’s allies in order to make the Dark Knight into a better warrior. At one point, Catwoman tells Joker that “you’re the one in love” with Batman, and Joker responds affirmatively, asking Catwoman, “isn’t that obvious?”
That’s a theme that continues with “Endgame,” a story with a climactic showdown between Joker (now claiming to be an immortal monster that has stalked Gotham City from the beginning) and Batman. After Batman is apparently fatally wounded, he does two surprising things: he asks the Joker to be with him in his final moments, and he tells his allies to stay away from him while he rests with his “friend.”
A distracted Joker gets injured by a falling stalactite, and the blood pooling between the two of them forms a heart showcasing their bizarre romantic bond.
While interacting with Catwoman, Joker often admits the real nature of his Batman obsession.
In terms of canonical events, we get another direct confirmation that Joker loves Batman in the Batman/Catwoman: Wedding Album special. During a knock-down, drag-out fight with Catwoman, Joker once again admits his love of Batman and even expresses confusion at the fact that Batman always chooses her over the Joker. This causes Catwoman to react with a purr-fectly catty response: “I’m…prettier than you.”
While those are the biggest canonical confirmations of Joker’s love for Batman, there are many more that occur in different continuities. The entire plot of the Lego Batman movie is driven by Joker wanting to hear that he is Batman’s “greatest enemy,” complete with innuendo-filled dialogue, such as Batman’s quippy “I like to fight around” when talking about Superman.
In the first issue of the excellent Batman: White Knight, Joker tells Batman they are a couple whose battles are excuses to see each other: “That’s our dynamic…All that’s missing is the make-up sex.”
Batman: White Knight is one of the best alternate universe Joker stories, and once again, the villain admits his love for the Caped Crusader.
Of course, it’s worth noting that Joker is a crazy killer with a deranged sense of humor, so all of these many references to loving Batman could be just one more way he’s trying to get under the Dark Knight’s skin.
Honestly, though, we love the idea that Joker really does romantically love Batman: it adds an extra layer of tension and drama to films like The Dark Knight, especially when Joker tells our titular hero, “you complete me.” And between Batman’s moral code and Joker’s romantic monomania, we know this fight between order and chaos will never truly end.