TORONTO — “I’ll warn you,” said director Todd Phillips as he introduced the first North American screening of “Joker” — “it’s f–king bonkers.”

The “Hangover” director is partly right: The final act of his new movie is, indeed, satisfyingly shocking, as Joaquin Phoenix’s Arthur Fleck sheds his sad-sack chrysalis and emerges, with requisite violence and gaiety, into full Joker.

For the rest of the film’s running time, at the risk of not joining the hyperbolic mobs on either side, I’ll say it’s … well, not bad.

This is no superhero movie. It’s a gritty drama about a schlub (Phoenix), saddled with a brain injury that causes him to cackle inadvertently, who’s caring for his ailing mom (Frances Conroy) and working a lousy gig as a rent-a-clown while nursing far-fetched dreams of being a comedian. He gets beaten up for being annoying — he lives in a hard-knock version of Gotham City — and then he gets beaten up again. Eventually, he pulls a sort of Bernhard Goetz move and guns down three Wall Street types who come after him on the subway.

If the casting of Robert De Niro as a late-night talk show host wasn’t enough to tip you off, this origin story is deeply rooted in the New York dramas of the ’70s, particularly “Taxi Driver,” “Death Wish” and “The King of Comedy” — the latter of which starred De Niro as a creepy stalker obsessed with a popular entertainer.

It’s an entirely different take on the DC comics character, and at the risk of angering the canon-bound fanboys, why not? Come on, who doesn’t want to see another movie about the Joker? He’s one of the choicest pop-cultural creations, an anarchic villain for the ages who’s still wide open for interpretation even after countless iconic portrayals. We all have our favorites — Heath Ledger’s mine, though I’ll never forget my first, Cesar Romero — but there’s no reason someone else can’t take a crack at it. And who better than crazy-eyed Joaquin Phoenix?

The actor’s physicality is something to behold. It’s never quite clear why Arthur’s so emaciated — at times he looks like he’s had a couple of ribs removed — but the way he contorts his spindly frame, and occasionally stretches it out into a joyful, Kabuki-esque dance, is mesmerizing.

Where Phillips and Phoenix come up short is in his sheer lack of charm. Arthur Fleck, despite his genuine pathos, really is irritating, and more than a little creepy.

Even his laugh — he has a laminated card that informs people it’s a medical condition — seems vaguely forced. The whole point of the Joker is that he gets bubbly joy out of the most horrible things in the world. To relegate his giggling to a neurological injury sort of defangs the concept.

There’s been some talk about “Joker” being inspirational viewing for potentially violent incels, which seems overheated. Movies are not the reason idiots are able to do horrible things. Also, Arthur catches the eye of his comely neighbor (Zazie Beetz), which rules him out of that category.

That said, Phillips does seem to sound a few notes throughout “Joker” that suggest his protagonist is a kind of folk legend. His subway murders spawn a “Kill the rich” campaign throughout the city, a riot of class warfare in which clown-masked mobs mobilize against the city’s elites. (In this, I suppose, Arthur Fleck has some common cause with Bane, the face-caged bad guy from “The Dark Knight Rises.”) Still, what is Phillips going for here? Joker as populist hero? Not sure how that sequel’s going to play, but then again, anything’s possible these days.

The director, in any case, had a solid defense in referencing the 1988 graphic novel “Batman: The Killing Joke” at the movie’s post-viewing Q&A. In it, the Joker says, “I prefer my past to be multiple choice.” He’s a slippery chameleon with a host of backstories. I don’t know if I’d choose to give this one first prize at a film festival, but it’s certainly worth seeing for Phoenix, whose mournful eyes and choking laugh perfectly embody his character’s lifelong query: “Is it just me, or is it getting crazier out there?”