What can you say about a guy who can’t stop laughing at his own jokes? Such is the plight of Arthur Fleck, whose miserable status is deepened by the fact that his jokes aren’t funny in the first place.

Perhaps you know Arthur by his professional name, which is also the title of this film: “Joker.” How did this pitiable individual get to be at the center of the most talked about movie of the fall? Hang on — you’ll die laughing.

“Joker” won the top prize at the prestigious Venice Film Festival a month ago, a controversial choice. This was followed by debate about whether the story’s revenge-fueled bloodshed might inspire copycat incidents, to the extent that Warner Bros. felt impelled to issue a statement emphasizing the movie is not “an endorsement of real-world violence.”

If only the movie itself were worthy of this kind of discourse. But “Joker” is a sour, incoherent jumble, redeemed only by Joaquin Phoenix’s astonishing performance in the central role.

The character, of course, is Batman’s cackling, green-haired nemesis in the DC Comics universe. We meet him as loner who works children’s parties dressed as a clown. Arthur lives with his deluded mother (“American Horror Story” regular Frances Conroy) in a dingy Gotham City apartment.

He dreams of being a stand-up comedian, and someday appearing on the popular talk show hosted by Murray Franklin (Robert De Niro). He also yearns for the single mom (Zazie Beets) living down the hall.

Both scenarios seem unlikely. Arthur’s painful inability to connect with people — or to even tell a simple joke — aligns him with the twisted anti-heroes of movies like “Taxi Driver.” “Joker” has strong affinities with another De Niro classic, “The King of Comedy,” which is also about a jerk who longs to make the world laugh (a movie that knows exactly what it’s doing, unlike “Joker”).

But however many films director Todd Phillips might be thinking about here, the real inspiration is closer to “Death Wish.” Arthur is a guy attacked by a dirty society — almost all the characters are mean or unfeeling — and what he really needs is a gun to help him fight back.

This fantasy is enhanced by doodads brought in from the DC world: Arthur’s flamboyant clothes, and a subplot about his connection to Thomas Wayne (Brett Cullen), the Gotham billionaire whose son is a little boy named Bruce.

Without its Batman connections, “Joker” would be a very strange movie for the multiplex, a relentlessly downbeat character study about a creep. For that reason alone, I wish Phillips (best known for the “Hangover” trilogy) had created something more thought-out.

As Arthur Fleck inspires Gothamites to tap their collective rage and riot in the streets, you realize that Phillips desperately wants to say something serious about These Times We Live In. But the film lashes out in too many directions, even as it glibly demonizes mental illness.

Phillips certainly has an eye for a grabby image — “Joker” is fun to look at, and I’ll not soon forget Arthur Fleck’s herky-jerky dance down an urban staircase.

Half of that is Joaquin Phoenix, who has spoken of inventing his performance day-by-day as the shooting went on. That’s certainly reflected in the movie: Even if the character doesn’t make sense, Phoenix thrillingly shows you an actor searching through the darker impulses of the human animal.

There’s a great sequence late in the film when Arthur — now in full Joker face-paint mode — struts on to the stage of De Niro’s talk show. His sudden confidence, the way he comes to life in the hungry eye of the cameras, is an astute comment about how a pathetic joker might become the star of an angry populist movement.

The movie can’t follow this up with any insight, unfortunately. But for a moment, Joaquin Phoenix gets the joke.

“Joker” (2 stars)

Joaquin Phoenix is astonishing as Arthur Fleck, a miserable would-be stand-up comedian who will eventually become the comic-book character called Joker. The film itself, directed by “Hangover” guy Todd Phillips, is a sour, incoherent jumble that wants to be taken seriously but doesn’t know how to get there. With Robert De Niro.

Rating: R, for violence, language

Opening Friday: Alderwood, Alderwood Mall, Cinebarre Mountlake Terrace, Everett Stadium, Galaxy Monroe, Marysville, Stanwood Cinemas, Meridian, Oak Tree, Pacific Place, Seattle 10, Thornton Place, Woodinville, Blue Fox, Cascade Mall, Oak Harbor Plaza

The poll to vote for your favorite Joker has been renewed to include Heath Ledger and Mark Hamill. Both were inadvertantly left out of the first version.