PHOTO BY HOPPER STONE / CTMG, INC.

Early in a chaotic dash to the world premiere of “Saturday Night Live,” a lighting rig crashes to the ground inches from a rehearsal in progress. As a crew member picks up a flaming spotlight, Garrett Morris stops him and lights a cigarette with the wreckage.

It’s an illustrative, if (probably) fictional, moment in the film “Saturday Night,” which tells the story of a landmark birth in spirit if not in literal fact. In the midst of the iconic show’s 50th season, the film is part of a longstanding effort to explain and mythologize something that has always added up to a cultural juggernaut greater than the sum of its sometimes-considerable parts.

The worthiness, or at least the interest, of that particular project will vary from viewer to viewer. But its effectiveness as a film is undeniable; like Morris puffing that chaos-sparked cigarette, it’s a madcap tale of comedy in the midst of madness, something that should never have worked and yet did — and sometimes still does.

Lorne Michaels (Gabriel LaBelle) is the main character here, but the film — directed and co-written (with Gil Kenan) by Jason Reitman, a scion of the show’s early legacy — resists the urge to overly inflate the show’s creator. Rather, Michaels is as much of an impediment to the show actually happening as anyone, refusing to compromise, delaying vital decisions and picking unnecessary battles while the scenery (or lack thereof) crumbles around him.

Many in the cast look, sound and perform well enough to be momentarily mistaken for the genuine article, none more so than Lamorne Morris, whose name and face will convince you that he must be Garrett Morris’ offspring. (He’s not.) Dylan O’Brien is also a dead ringer for Dan Aykroyd, not only in looks but in oddball charm, and Ella Hunt steals scenes as effortlessly as Gilda Radner could, even providing a measure of melancholy in the right moments; you’ll get a chill when she speculates about what she and John Belushi (Matt Wood) will be up to in 20 years.

Not every thread pans out, as some characters (and one llama) are introduced mainly to shoehorn a bit of “SNL” lore into the proceedings; other inclusions are simply bizarre, as they both interrupt the flow and are not based in reality. (Why J.K. Simmons is here as a pants-dropping Milton Berle, I have no idea.) But “Saturday Night” is a triumph of pacing and design and a lovely time, especially for comedy nerds.

I still don’t know why they kept using the bee costumes, though.

My Rating: 7/10

“Saturday Night” is now playing in theaters.