Live from New York, it's the year's biggest cinematic surprise: Jason Reitman’s Saturday Night!

This dramatized (and largely fictionalized) look at the chaotic 90 minutes before the first episode of Saturday Night Live in 1975 zips along with a pace as coked up as its cast of future superstars, a tempo that saves it from being as corny and didactic as it could have been, even in hands as generally talented as the co-writer/director's.

As Lorne Michaels (Gabriel LaBelle, The Fabelmans) winds his way through 30 Rock, putting out real and metaphorical fires, Reitman's and Gil Kenan’s script reveals the essence of the cast and crew’s major players. True to the countdown situation at hand — which nearly plays out in real time — there's little space to delve into what makes John Belushi (Matt Wood) or Gilda Radner (Ella Hunt, Anna and the Apocalypse) tick, and yet a massive coke snort here and radiant comedic confidence there reveal plenty about the respective performers in organic fashion.

While it's a joy to witness so many young talents on the cusp of fame, the filmmakers refuse to lionize anyone, presenting their faults in tandem with their gifts and charms. And though Reitman and Kenan perhaps go too far in their takedown of Chevy Chase (Cory Michael Smith, May December), the prescient critique that writer Herb Sargent (Tracy Letts) pours atop the egotistical actor provides one of the film’s biggest laughs.

However, smiles and yuks are the constant of Saturday Night and receive an extra boost whenever Nicholas Braun appears in a dual turn as Andy Kaufman and Jim Henson. But the extent to which the material brings out the best of this surprisingly carefully curated ensemble is a delight to experience.

There's little in Dylan O’Brien’s body of work to suggest he’s capable of his blustering take on Dan Aykroyd; Rachel Sennott is finally tolerable (but still not great) as writer Rosie Shuster; and Lamorne Morris acquits himself of Fargo S5’s drudgery with an excellent portrayal of Garrett Morris (no relation), whose late musical moment with Billy Preston (Jon Batiste) and his band is a highlight among the film's numerous highlights.

It all coalesces within Jess Gonchor’s thoroughly convincing production design that makes it feels like a time machine has been employed. Now, if only recent casts of SNL could likewise transport back and learn a thing or 37 from their predecessors, we’d really be in business.

Grade: A-minus. Rated R. Now playing at Carolina Cinemark and Regal Biltmore Grande.

(Photo: Sony Pictures)