In the latest DC Comics blowout, Ezra Miller suits up as the speedy superhero alongside special guests like Batman (hello, Michael Keaton).The Flash, the latest DC Comics superhero to get his very own big show, isn’t the outfit’s usual brooding heavyweight. He’s neither an old-style god nor new (a.k.a. a billionaire), but an electrified nerd who joined the super-ranks by accident, not by birthright or by design. Out of uniform, he is a normie, a goof and kind of endearing. He’s really, really fast on his feet, you bet. But what makes him pop onscreen is that when things go bigger and grimmer here, as they invariably do in blowouts of this type, he retains a playful weightlessness.That’s a relief, particularly given how the movie tries to clobber you into submission. Big action-adventures invariably give the viewer a workout, smacking you around with their shocks and awesomeness, though it sometimes feels as if contemporary superhero movies have taken this kind of pummeling to new extremes. That may be true, though movies have long employed spectacle — pyrotechnics, lavish set pieces — to bait, hook and bludgeon the audience so it keeps begging for more. If the bludgeoning feels more inescapable these days, it’s partly because the major studios now bank so heavily on superhero movies.“The Flash” is one of the more watchable ones. It’s smartly cast, ambitious and relatively brisk at two and a half hours. The story tracks Barry Allen (Ezra Miller) and his superhero persona, the Flash, as he whooshes, wrapped in tendrils of lightning; traverses space-time continuums; and tries to exonerate his father (Ron Livingston), who’s in prison for killing Barry’s mom (Maribel Verdú). As is usually the case with superhero movies, the story is nonsensical and convoluted — it’s no wonder a character uses a tangle of cooked spaghetti to try to explain a major plot point — but not calamitously so. The overall vibe is upbeat.Some of that liveliness comes from Miller, a tense and almost feverishly charismatic presence. (Their well-publicized offscreen troubles hang like a cloud over this movie.) Some of the Flash’s appeal, of course, is also baked into the original comic-book character, “the fastest man on Earth,” who first hit in 1940 (via creators Gardner Fox and Harry Lampert) and was revamped (by Robert Kanigher and Carmine Infantino) in 1956. Five years later in Issue No. 123, these versions of the Flash (there are others) discover that they exist on two seemingly separate Earths, an idea this movie, well, runs with by introducing parallel DC Comics realms.It’s a conceit that pays off the second a shambolic Michael Keaton makes his entrance as a graybeard puttering about a near-derelict Wayne Manor. Having hung up his Bat-suit in his reality (while DC has repeatedly rebooted the franchise in ours), Bruce appears to have entered the Howard Hughes chapter of his cosseted life when Barry drops by. Long story short, the two rapidly join forces, dust off the Batcave tech, furrow their brows and suit up, as other members of the DC stock company join the party, including Alfred Pennyworth (Jeremy Irons), General Zod (Michael Shannon) and Supergirl (Sasha Calle).The entrance of these company players are timed like special-guest appearances — ladies and gentlemen, Zod the Zaniac! — and they’re obviously meant to delight true believers. To a degree, they also feel like they’ve been brought in to shore up the Flash during his first stand-alone outing. Cramming the screen with established names to hedge their expensive bets is an old-fashioned studio gambit, whether in a 1920s musical revue or 1970s disaster flick. Whatever the rationale here, the results are amusing, and it’s especially nice to see Keaton, who first played Batman in Tim Burton’s 1989 film. He seems to be having a good time, and when he looks in the mirror approvingly, it’s easy to share in his self-admiration.Working from a script by Christina Hodson, the director Andy Muschietti keeps these pieces greased and quickly moving, though he almost blows it as soon as the movie begins. It opens with an unfunny protracted bit in which Barry, who’s late for work, orders a sandwich from a pokey server. (That the first villain in the story is a service worker is a choice.) While the guy readies the order, Barry turns into the Flash to help his world’s Batman (an uncredited Ben Affleck) dispatch some villains. It goes as expected — bam, splat — but then a hospital wing collapses, and newborn babies go flying, hurtling toward the street.It’s a creepy setup that Muschietti milks for laughs that become queasier and ickier the longer and the more gleefully flamboyant the scene plays out. It’s absurd, outrageous, digitally fabricated and needless to say the Flash will save the day. The problem is that Muschietti, who has a talent for fraying your nerves with images of child endangerment (as he showed in the “It” horror flicks), is so obviously pleased with these airborne babies that he keeps showing off (turning a microwave into a bassinet), which drains the sequence both of its outlandish comedy and of any tension that might make the Flash’s heroism resonate.The movie more or less recovers, settling into its lively groove, even if the Flash remains a curiously uncertain presence. Surrounding him with bigger superheroes may have made branding sense, but the net effect is that the movie never persuasively establishes the Flash as a confident stand-alone entity. That may make the question of Miller playing him in the future moot. Who knows? Last year, Miller apologized for their behavior and said they were seeking treatment for “complex mental health issues.” I liked “The Flash” well enough while watching it. But thinking and writing about it and everything that has gone down has been dispiriting — real life has a way of insinuating itself into even better-wrought fantasies.The FlashRated PG-13 for superhero violence. Running time: 2 hours 24 minutes. In theaters. More