WARNING: The following contains spoilers for director Todd Phillips' Joker, in theaters now. 

Everybody's talking about Joker. And as is the tradition with most movies featuring comic book characters, talk of a possible sequel has begun. Joker's star, Joaquin Phoenix, is potentially open to reappearing as the titular character, if slightly hesitant. But director Todd Phillips has said repeatedly that this film was conceived as a standalone story, independent even of the character's roots in the comics.

The movie was approached as an Elseworlds tale that, in comic form, would almost certainly have been published under the more adult DC Black Label imprint, which seems to be establishing a standalone DC universe with titles like Batman: Damned and Harleen. So, it's possible that Joker could set up a timeline for the upcoming 2021 The Batman from director Matt Reeves or for a Joker sequel.

But it probably shouldn't.

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Some things are just not meant to have sequels. In comics, Frank Miller's Batman: The Dark Knight Returns was unceremoniously followed by Miller's sequel, Batman: The Dark Knight Strikes Again in 2001 -- 15 years after its seminal predecessor.

Dark Knight Returns is to comics what films like Casablanca, Citizen Kane, Apocalypse Now, and A Clockwork Orange are to cinema. While sequels may have been proposed for some of these legendary movies, they never saw the light of day. So, they remain iconically frozen in time as once-off masterpieces that, each in their own way, changed cinema forever.

The same could be said for Dark Knight Returns and comics. Frank Miller simply didn't have it in him to create a follow-up to DKR that could ever top - or even match - the impact the original had. When readers picked up The Dark Knight Strikes Again, they were hoping for more of the same. Instead, they got shaky, sketchy artwork and deliberately "grim & gritty" writing that felt like a pale imitation of the original.

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Joker is a genre-busting movie that tells the tale of a society that is devouring itself, and one man's journey through the uniquely constructed insanity that helps him survive. A very important part of Joker's mystique and appeal is that it is completely open-ended. Three-quarters of the way through the film, it's revealed that much of what we were led to believe up until that point, was all in Arthur Fleck's head.

This begs a few questions. Even though the world that Joker takes place in is very dark, just how plausible is it that, following Arthur Fleck's murder of the obnoxious and violent stockbrokers on the train, an entire movement of clown-faced supporters would rise in support of a murderer? And the anti-elitist "Kill the Rich" sentiment that follows the murder on the train is a fitting metaphorical slogan. But it's a lot more frightening when taken literally.

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There's also the question of Thomas Wayne. Historically - with just a few exceptions, like Batman: Damned and, of course, Joker - Bruce Wayne's dad has been painted as a saintly philanthropist who served as an inspiration for Batman's altruistic motives. In Joker, he's an aggressive, capitalist villain, who punches Arthur Fleck in the face, revealing to the protagonist that his mother is delusional and crushing any hope he might have had of finding a normal family connection.

Could it be that the Thomas Wayne and Arthur Fleck meeting is a fabrication of Fleck's elaborately delusional world? Wayne comes across as a caricature that represents everything bad about the rich. Maybe this is just another perspective on him. But then again, maybe it isn't.

Beyond that, is the Joker character even real? The final moments of the film see the rioting, clown-faced masses hailing Joker as a hero while he stands on the hood of a wrecked police car. Again, dark though the world of Joker may be, these people aren't even slightly put off by the fact that the man they're cheering for just committed a gruesome murder on live TV.

The Joker stands in front of a burning car in Joker.

In the closing moments, Arthur Fleck is in a mental asylum, completely out of context from the riot scene, with no narrative of how he got there. This leaves the final open-ended question: Is any of this real? The entire point is, we don't know. And neither, it seems, does Arthur Fleck himself.

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Batman: The Killing Joke by Alan Moore and Brian Bolland is one possible origin for the Joker. While Heath Ledger's Joker's varying accounts of how he got his scars suggest a few other possible origin stories. The Joker is deliberately ambiguous. And he may not even know himself just how he came to be - or even if the world he's constructed around him is real. So, Batman himself could even be an imaginary construct in his world.

The ambiguity and lingering questions viewers are left with at the end of Joker are meant to remain exactly that. Todd Phillips and Scott Silver's Joker is more a commentary on how society fails the downtrodden than a linear origin story. It's a standalone descent into madness that would be watered down if any of the questions it leaves you with were to be answered in a sequel. And it could or could not be a Joker story at the same time.

Besides that though, it's very true to the Joker character. You're not supposed to know who he truly is. If Joaquin Phoenix were to return as Joker, in a sequel or even in one of the upcoming Batman films, it would make the character real. And the best thing about Joker in this movie is that you'll never know if he exists or not.

Directed by Todd Phillips, Joker stars Joaquin Phoenix, Robert De Niro, Zazie Beetz, Bill Camp, Frances Conroy, Brett Cullen, Glenn Fleshler, Douglas Hodge, Marc Maron, Josh Pais and Shea Whigham.

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