Warning: This article includes major spoilers for "The Batman."

From Alfred Stryker to The Riddler, Batman has always had a compelling set of supervillains to fight against. Bruce Wayne's alter ego was born to fight crime in Gotham, and without his home being a lawless city overrun by criminals, there could be no Batman. This means that Batman's supervillains are just as important to his existence as a superhero.

In the DC Universe, the caped crusader's enemies have had many interpretations. Christopher Nolan offered a fresh and utterly original take on the Joker, with Heath Ledger nailing every mannerism of Gotham's Clown Prince of Crime, right down to his cunning laugh. In "The Batman," director Matt Reeves' iteration of The Riddler is a man of smart and psychopathic intellect, who appears to be dangerous and terrifying the second he makes eye contact. It gets you thinking — in this new, rain-soaked, gritty version of Gotham, does the Joker have a place of his own?

The answer to that question comes in the form of a cameo at the end of "The Batman." First you hear a voice. You begin to recognize that this character's colorful language. The dark, recurring laughter, and the tendency to use clown metaphors can only mean one thing — it is the Joker. When the screen goes black, it gets you thinking: Is it really a superhero movie if you're not setting up a sequel? And what better way to do that than by way of its villain?

Is That You, Clown Prince Of Gotham?

Towards the end of "The Batman," after Riddler has been escorted to his private cell at Arkham Asylum, he discovers that he isn't exactly enjoying his solitude. Maybe he misses his Internet friends. Perhaps he's mourning his non-existent friendship with the Batman. Anyway, the Riddler is pretty unhappy about his situation, until a fellow prisoner indulges him in the one thing he loves most: riddles. What's more interesting is that we don't clearly see the person behind the voice — just the side of his face through a small window in the cell door. The answer to the riddle he asks, of course, is "friend," teasing that the Riddler has a dangerous new mind to collaborate with.

This version of the Joker is played by actor Barry Keoghan ("Eternals" and "Killing of a Sacred Deer"), who was previously announced to have been cast as police officer Stanley Merkel in "The Batman." In an interview with IGN, the director shared that he devised a plan to conceal Barry Keoghan's true association with the film — and even shot fake scenes to protect the reveal (candid set photos showed Keoghan dressed as a cop). Matt Reeves was worried fans would speculate about the film exploring the Joker, so he did his best to keep it a surprise.

"When you're making a movie like this, you want it to be different, you want people to feel like they're having a special experience. And then for me, when you're going to the cinema you want some level of surprise. I think one of the things I was worried about was speculation while we were making the movie, that we would be exploring the character that we ended up exploring. So we started thinking what we could do to throw people off that scent. This idea of making him Stanley Merkel was exactly that, because the police force is actually a big part of the story so it seemed credible that we could be doing that."

When the credits roll, you'll see that Keoghan is credited as "Unknown Arkham Prisoner" — which fits with the enigmatic nature of the scene, and also probably went some way towards helping keep the true nature of Keoghan's character a secret. Now, the truth has been unmasked.

"The Batman" is in theaters.

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