Joker's Entire Reputation Is Built On One Terrifying Rule
As the Clown Prince of Crime, The Joker often finds himself collaborating with the biggest criminals within DC's underworld. If a huge scheme is happening in the DC Universe (be it against Gotham City, outside of it, or the entire universe itself), expect The Joker to be at the heart of it all. This is interesting considering The Joker's tendency to typically kill off his allies and partners, not for any particular reasons beyond his own amusement and preserving his reputation.SCREENRANT VIDEO OF THE DAY
On paper, The Joker's clear insanity and perchance for chaos means that he doesn't play well with others. And yet, time and time again, he gets offers to join in on the biggest plans, often being placed as a key member of DC-wide villain groups like the Injustice League and the Legion of Doom. But...why? Why does he always get a seat at the table when geniuses like the Legion of Doom are making their dark plans? Why did Lex Luthor let him in on his plan to conquer reality for Perpetua? Why do Gotham's other villains bend over backward to facilitate his plans?
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Readers learn the answer in Infinite Crisis #7 by Geoff Johns, Phil Jimenez, George Pérez, Ivan Reis, and Joe Bennett. The Joker tracks down and kills Lex's son Alexander Luthor, Jr. because Lex refused to allow him into the Secret Society of Super Villains. Lex Luthor's decision to exclude is understandable as The Joker is too unpredictable to be a part of the plan. However, therein lies the dilemma that most villains face and why so many villains work with The Joker despite his unpredictability: they know that Joker will kill anyone who won't let him play with them.
The fact of the matter is that most DC villains fear The Joker as everyone has seen the kind of damage he can do to heroes who directly oppose him. So, on one hand, a villain who simply gets in his way risks being violently killed and, on the other hand, if a refuses to let The Joker participate in any of their crimes, they are sure to be killed in the cruelest way possible. It ends up becoming a sick, catch-22 situation in which no one really wins except The Joker.
Basically, The Joker's mind works like a child—a homicidal child—when other children don't let him play their games. When he's not included, he gets offended and seeks to punish whoever has excluded him. Alexander Luthor Jr., unfortunately, learned this the hard way. So, kills like these serve as a warning: if you don't let The Joker play, you'll most certainly end up dead.