Anybody who’s ever brewed a coffee to stay up and watch NBC's “Saturday Night Live” will appreciate the caffeinated buzz of “Saturday Night.”

Director Jason Reitman’s breakneck comedy (★★★½ out of four; rated R; in select theaters now, nationwide Friday) is a fictionalized account of the 90 chaotic minutes before the first “SNL” episode went on air in 1975. (Its Friday wide release is 49 years to the day after the show's premiere.) The film's a bit haphazard at first, as frazzled producer Lorne Michaels (played by outstanding “The Fabelmans” breakout Gabriel LaBelle) tries to keep this sketch-comedy experiment from turning into a spectacular crash-and-burn. But instead of slowing down, you get used to its speedy pace, enough to sit back in awe of the indisputable acting talent – familiar names and fresh faces alike – Reitman’s pulled together to revisit a TV miracle.

The tick-tock starts at 10 p.m., as Michaels juggles a busy studio full of stand-up comedians, musical guests, his 20-something Not Ready for Prime Time Players, guest host/iconic crank George Carlin (Matthew Rhys) and other assorted oddballs, all while he doesn’t really know what the show even is. That worries late-night programming guru Dick Ebersol (Cooper Hoffman), who’s trying to keep fellow NBC executive (Willem Dafoe) from airing a rerun of Johnny Carson’s “Tonight Show” at the last minute instead.

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Mishaps abound: A lighting fixture almost takes out John Belushi (Matt Wood), who still hasn’t signed his contract and is a major cause of Lorne’s stress. Mercurial funnyman Andy Kaufman (Nicholas Braun) wanders around aimlessly while “Muppets” puppeteer Jim Henson (also Braun) wonders where his script is. Head writer Michael O’Donoghue (Tommy Dewey) battles with a no-nonsense network censor (Catherine Curtin). Two cast members, opera-trained Garrett Morris (Lamorne Morris) and commercial veteran Jane Curtin (Kim Matula), wonder what they’re even doing there in the first place.

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“Saturday Night” hinges on LaBelle’s strong performance. Although we all know “SNL” turned into a pop-culture phenomenon, now celebrating its 50th season, we care about Michaels' sanity making it through a night full of increasingly daft obstacles, including angry phone calls from an irate Carson and being on the business end of a fake blood sprayer.

Reitman’s casting is top-notch across the board, especially in finding people to really play comedic legends and not just imitate them. Cory Michael Smith, best known as the Riddler on TV’s “Gotham,” nails the macho bravado and underlying insecurity of Chevy Chase. Dylan O’Brien and Ella Hunt inhabit the rascally charms of Dan Aykroyd and Gilda Radner, respectively. Morris matches his real-life counterpart’s easy swagger, while national treasure J.K. Simmons chews up the scenery as Milton Berle. And while no performer since has captured anything close to Belushi’s electricity or gift for physical comedy, Wood wonderfully channels the "Animal House" star's unpredictable energy.

Reitman and Gil Kenan, who teamed up to write the film’s crackling script, have been in charge of rebooting the “Ghostbusters” franchise, but “Saturday Night” is truly their nostalgia fest.

Performers like O’Brien and Hunt could bring in younger fans who’ve never seen those early “SNL” episodes, but the movie will mean the most to those older folks who grew up in the show's early boundary-pushing years or remember seeing Kaufman’s hilarious “Mighty Mouse” riff or Garrett Morris’ song stylings – both referenced to a rousing degree in the film – back in the day. (Reitman’s outing is also consistently funnier than any “SNL” episode of recent memory.)

“Saturday Night” is a throwback to an infamous night that could have easily been a disaster but somehow ended up a triumph, and an ode to the magic that happens when youthful creativity meets unabashed crazy.