When it debuted 50 years ago, “S.N.L.” was chaotic, rangy, even offensive. But nothing’s wild or crazy in Jason Reitman’s fictional reimagining of its first episode.Movies about tectonic cultural shifts tend to be too neat and tidy, too frictionless. “Saturday Night,” the director Jason Reitman’s fictional reimagining of the debut of “Saturday Night Live,” is a nice, safe movie about a revolution. Busily plotted and sporadically funny, it is a backstage look at the night a gang of comics whom most of the world had never heard of began taking over TVs across the country. It was a comedy home invasion on a national scale, and it was glorious (when it didn’t suck).The movie, written by Reitman and Gil Kenan, has a straightforward conceit. It opens at on Oct. 11, 1975, the night that the show, then called “NBC’s Saturday Night,” is scheduled to debut. (The name was changed in 1977.) In just 90 minutes — ticktock — the show will go live if the performers, writers, crew, network suits and some guy named Lorne can get it together in time. A lot of money, reputations and possibly bright futures are riding on the show, but with its deadline looming, it still seems underbaked and, from some vantage points, overly abstract.To convey that premiere and what it portended, Reitman both sticks to the historical record and embellishes it, building momentum by zeroing in on some mini-crisis amid rapid edits, swish pans and rushing bodies. Everything and everyone at 30 Rockefeller Plaza runs too fast or seems immobilized, with characters either in frenetic motion or huddling in pools of flop sweat. As the minutes pass, Reitman periodically cuts to a clock onscreen or someone calls out the time; at one point, a set designer, Leo Yoshimura (Abraham Hsu), slowly begins installing bricks on the stage of Studio 8H, each brick an emblem of the show’s parts sliding into place.In a (real) 1975 news release, NBC called the show “a new concept in late-night programming.” The network wanted a replacement for weekend reruns of “The Tonight Show Starring Johnny Carson,” and this venture was going to be a comedy show with sketches, musical guests, short films and the Muppets. But it was unclear what it was, maybe even to those behind the scenes. That much seems obvious when an NBC executive, Dick Ebersol (Cooper Hoffman), asks the show’s creator-producer, Lorne Michaels (Gabriel LaBelle), if he knows what it is. The straight-faced Lorne responds with an amusing, self-aggrandizing analogy involving Edison, the lightbulb and electricity. Who are you in this metaphor, the baffled exec asks.Lorne doesn’t answer, but the movie does by making him its focus. The character is less interesting than his surroundings — he’s more a blurry place holder than a fully realized personality — but whether here or there, Lorne is the center of this storm. He’s the hub, the visionary, the guy who can see past the chaos. Sure, there’s his wife, the writer Rosie Shuster (a tart Rachel Sennott); the host, George Carlin (Matthew Rhys); and a creepy suit, Dave Tebet (Willem Dafoe, in by far the funniest turn). But the star is Lorne because even genius apparently needs a boss.So, hi Chevy Chase (Cory Michael Smith), Gilda Radner (Ella Hunt), Jane Curtin (Kim Matula), Laraine Newman (Emily Fairn), Dan Aykroyd (Dylan O’Brien), Garrett Morris (Lamorne Morris, no relation) and John Belushi (Matt Wood). It’s nice to see them, so it’s too bad that only a few of the actors playing the main cast — and only the men — manage to register. That’s the case even when Reitman gestures at the show’s gender problems, as in a peek at a still-funny sketch about female construction workers learning how to harass a guy in short shorts. It’s Dan’s squirmy embarrassment, and how he then wags his rump, that makes it work.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More