Saturday Night mild? Jason Reitman's SNL recreation doesn't quite match the original's rebellious spirit

It's time to put on makeup It's time to dress up right It's time to get things started Why don't you get things started?

Watching the backstage bedlam of Jason Reitman's Saturday Night made me think of The Muppet Show.  

And it's not because the film throws my beloved Jim Henson under the bus, portrayed here by Nicholas Braun as a prudish hippie getting pranked by the Saturday Night Live staff.

It's because the entire conceit of Saturday Night, which shows us the 90 minutes before the first episode goes to air, plays like a live-action version of The Muppet Show, complete with special guest stars (a disgruntled George Carlin) and a plethora of subplots: Is Chevy Chase's ego too big for the cast? Will John Belushi sign his contract?

Not to mention Lorne Michaels — the Kermit of this analogy, waving his arms frantically in the air — the Canadian comedic wunderkind trying to convince NBC to risk 90 minutes of air time on a group of unknowns. 

The film is the latest from director Jason Reitman, son of director Ivan Reitman, who burst onto the scene with zippy caustic comedies such as Up in the Air and Juno. Oscar bait for voters, those movies announced Reitman as an exciting new Hollywood auteur. 

But in the past few years he has disengaged with the present in favour of an extended spelunking of nostalgia, from his Gary Hart movie The Front Runner, to his reanimation of his father's Ghostbusters franchise, directing Ghostbusters: Afterlife and executive producing Ghostbusters: Frozen Empire. 

Sticking firmly to the past, Saturday Night is a ticking clock of a film set in real time on Oct. 11, 1975, during the last 90 minutes before the show goes live for the first time. 

The network is embodied by Willem Dafoe as NBC's head of talent, Dave Tebet. Costumed in a sharp suit and spectacles, Tebet's shallow smile suggests there's little faith in the experiment. There's already a tape of a Tonight Show rerun cued up if Michaels fails.

Reitman and co-writer Gil Kenan illustrate the changing of the guard with J.K. Simmons appearing as Milton Berle, a relic from the so-called golden age of television when millions would tune in to watch Uncle Miltie. 

Simmons is in high camp here, one moment doing the cha-cha with chorus girls, the next marking his territory by whipping out his legendary schlong for shock effect. 

Not that this version of SNL is genteel. If anything, what Reitman and the cast channel is a gonzo sort of energy. The backstage at studio 8H, with its serious summer camp vibe, is a realm of barely contained chaos.  

Indeed, one of the most successful aspects of Saturday Night is the inspired casting that uses a great mix of modern emerging talents to portray the fresh faces who would soon become famous. 

Cory Michael Smith's version of Chevy Chase vibrates with ambition and arrogance. Nicholas Podany's Billy Crystal is sexy, smart and sad. Ella Hunt as the singular Gilda Radner has just a few moments, but channels a playful spark.  Dylan O'Brien's Dan Aykroyd is goofy and endearingly awkward. Tommy Dewey as head writer Michael O'Donoghue is a sharp-tongued assassin.