Ezra Miller turns out to be every bit as on-the-spectrum manic, antsy, and impulsive as you’d expect in a stand-alone film about “The Flash.”

He gives us a comic book character with issues and an agenda, two distinct and noticably different versions of that character in a movie that’s an origin story without being an origin story, and a multiverse movie that’s actually about time travel as well as timelines.

This history-altering, Butterfly Effect-impacting, consequences of changing the past tale is as loaded with pandering fan-service as any recent comic book adaptation. It’s jokey, but a pretty good percentage of the laughs don’t land. Some of the casting is gimmicky and other pieces don’t quite fit in the puzzle — yet.

But Miller times two, complemented with a bracing, world-weary turn by Michael Keaton as a Batman who’s moved on but not traded cars, and a story with consequences and pathos give this genre outing an edge your typical DC Universe picture lacks. It’s damned interesting, and that goes for the characters, too.

Barry Allen’s an impatient coffee shop customer, impatient forensics researcher and resigned to being “the janitor of the Justice League,” the guy Bruce Wayne’s butler Alfred (Jeremy Irons) phones when Batman (Ben Affleck) is busy, in mid-motorcycle chase, when Superman’s otherwise engaged and when Wonder Woman is running late.

“SOMEbody has to save the rest of the world” when the grownups are Busy, Batman tells him.

As The Flash, Barry can bolt between his native Central City to Gotham or Metropolis when the need arises. And with a hospital falling into a sinkhole and a maternity ward collapsing, sending babies and the on-duty nurse tumbling (“Baby Shower!”), The Flash is the only guy who moves fast enough to stop time and pluck babies, nurse and a support dog from the air before they tumble a hundred feet to the ground.

Barry’s particularly distracted these days, struggling to prove his father’s (Ron Livingston) innocence in the murder of his mother. That preoccupation is how he stumbles into his ability to run so fast that time doesn’t just slow down and stop. It can go backwards, allowing Barry to travel back in time to concievably save his mother’s life, his father from prison and himself from growing up motherless and under the cloud of his father’s imprisonment.

Bruce Wayne can warn him all he wants about the nature of time, The Butterfly Effect and all of that. Barry figures saving three lives is worth the risk.

But the moment Barry intervenes in the past, his “present” is out of bounds and he finds himself trapped in a timeline where Mom is alive, and he can’t help but run into his chattering, dopey and annoying college-freshman self.

He’s messed up. There is no Justice League. Batman’s disappeared. Superman is unknown. And the Man of Steel’s Kryptonian menace, General Zod (Michael Shannon) and his minions have shown up to find Kal-El and destroy Earth in the process.

There’s nobody to stop them but The Flash, and Barry and General Zod have shown up at the point in time where Barry “gets his powers.”

So we’ve got flashbacks that not only show us Barry’s childhood. That’s where this script hides the “origin story” in plain sight. And now Barry has to rewrite that origin story following the original script of his life as closely as he remembers it he wants other Barry to be of use in the fight to come.

The Flash sprinting effects are impressive, and the learning curve scenes — Barry instructs “Barry” on how to be a Flash — means lots of sight gags and stumbles as somehow, they must reconstruct as much of the Justice League as possible on an Earth that never enjoyed the full benefits of superheroes, and that embraced Eric Stoltz as the original Marty McFly of “Back to the Future.

Even as the movie bogs down in effects and exposition in the middle acts, Miller keeps us amused and engaged with two versions of this clumsy, foul-mouthed kid and adult trying to do the right thing, and reason out what the right thing might be.

Affleck, Keaton and Irons are the supporting players who make an impresssion. Kiesey Clemons, playing the Flash’s college-classmate love interest, in wasted in this film, as is Shannon reprising a villain we’ve already taken the measure of.

The hard, unbending truth of this summer’s critical mass of recycled popcorn pix is that unlike the enduring representatives of that genre, these don’t merit of stand up to a second viewing. Marvel, DC, “Transformers” Freightliner of “Fast X” Diesel, once the novelty of being pandered to has worn off, that’s it for anybody who isn’t deep into their subcultures.

Director Andy Muschietti of the “It” movies tries to keep “Flash” moving and generally succeeds, although one gets the impression he and the suits were so overwhelmed at how cool the effects look that they wouldn’t cut a minute, and this blinkered narrative — as novel as it is in its approach to well-worn comic book plot points — could stand some trimming.

With Miller, the viewer can’t really separate the art from the troubled artist because the performance and the characters he’s playing won’t let us. But that never takes you out of the movie, and the film’s earnest “Save others” ethos and “Don’t relive your past, live your life” messaging resonates.

The cameo gimmick sweeping over comic book moviedom these days is played to the max here, with actors making an appearance, often without their physical presence on the set. No, the fascimiles of earlier incarnations of superheroes aren’t the most convincing CGI replicas ever.

But “The Flash,” while it never comes close to the gee whiz “I can do THIS?” novelty of the many Spider-Man “origin” iterations, makes a charming, nostalgic and sometimes touching addition to the genre, and lets us hope Miller will recover enough to return to acting this character and others.

If Robert Downey made the most of a second chance, anybody can.

Rating: PG-13 for sequences of violence and action, some strong language and partial nudity

Cast: Ezra Miller, Kiersey Clemons, Michael Keaton, Michael Shannon, Sasha Calle, Antje Traue, Ron Livingston, Jeremy Irons, Temuera Morrison and Ben Affleck

Credits: Directed by Andy Muschietti, scripted by Christina Hodson, based on the DC Comics character. A Warner Brothers release.

Running time: 2:24