Taking cues from the golden era of Aaron Sorkin-esque “walking and talking,” the biographical comedy film “Saturday Night” depicts the turmoil of launching the 1975 premiere episode of “Saturday Night,” later renamed “Saturday Night Live.”

Director and co-writer Jason Reitman (“Juno,” “Up in the Air”) unspools the story in real time, following show creator Lorne Michaels (“The Fabelmans” breakout Gabriel LaBelle) as he attempts to wrangle his unwieldy cast, solve a myriad of technical issues and convince a skeptical network exec (Willem Dafoe) to allow the show to make it to the airwaves.

The script by Reitman and frequent collaborator Gil Kenan takes several true-to-life stories from the development of “SNL,” embellishes a few others and consolidates the mayhem to fit the real-time conceit of the film. The congested structure requires a grounded and compelling lead figure, which LaBelle more than delivers as Michaels (without leaning too hard into impersonating his well-known voice).

“Saturday Night” also anchors the LaBelle performance with two other meaty supporting roles — Rachel Sennott (“Bottoms”) as show writer (and Michaels’ then-wife) Rosie Shuster and Cooper Hoffman (“Licorice Pizza”) as network exec Dick Ebersol. Michaels’ interactions give “Saturday Night” narrative conflict beyond Michaels’ attempts to stage an untested TV concept.

The film zooms around the studio running into all sorts of familiar personalities, almost all of them uniformly memorable. The list includes Dylan O’Brien as Dan Aykroyd, Matt Wood as John Belushi, Lamorne Morris as Garrett Morris, Ella Hunt as Gilda Radner, Cory Michael Smith as Chevy Chase, Kim Matula as Jane Curtin and Nicholas Braun performing impressive double duty as Andy Kaufman and Jim Henson. J.K. Simmons pops in for a couple of wickedly funny scenes as Milton Berle. The entire cast is uniformly excellent, though moviegoers unfamiliar with real-life people may find the parade of faces to be overwhelming.

For most of its runtime, Reitman stages a convincing case that all this insanity really did happen in the 90 minutes preceding the first show. The film’s pristine technical execution helps to propel that illusion, particularly through Eric Steelberg’s cinematography and music by Jon Batiste (who also appears in the film as musician Billy Preston).

Sadly, the film stumbles a bit in its final stretch, as Reitman stages a disjointed and unconvincing showdown between Michaels and exec David Tebet (Dafoe). Maybe this conflict is true-enough to life, but the execution breaks the spell of the movie at the precisely wrong moment.

Fortunately, those uninspired 10 minutes can’t derail the strength of the overall film. For fans of “SNL” in the early years, or for anyone still itching for “West Wing” level walking and talking drama, “Saturday Night” hits enough of the mark.

•••

Tyler Wilson can be reached at twilson@cdapress.com.

    This image released by Sony Pictures shows a scene from "Saturday Night."