Classic pieces of cinema have a way of becoming sacrosanct — like holy texts that are meant to be studied and revered, but never questioned, and certainly never parodied. Still, though, Alfred Hitchcock's much acclaimed early spy thriller The 39 Steps from 1939 is ripe for mockery.

The 39 Steps, the stage comedy, played both on and off-Broadway and in London's West End for the better part of nine years, beginning with the London premiere in 2006. The version that SF Playhouse is doing, which opened on Wednesday, is a rollicking, slap-stick clowning affair, that is English comedian and playwright Patrick Barlow's adaptation of an earlier four-person stage version by Simon Corble and Nobby Dimon.

It is a master class in farce and physical comedy for any actor, and the four actors in the main cast at SF Playhouse (there are also four understudies), are all extremely talented comedians. Phil Wong plays Richard Hannay, the Canadian expat in London who gets wrapped up in a very Hitchcockian drama, being falsely accused murder and having to go on the run and clear his name at the same time. (Film buffs will recognize a fair bit of overlap with North By Northwest, which was Hitchcock's sort-of Americanized remake of The 39 Steps starring Cary Grant.)

The plots of Hitchcock films, boiled down and summarized, can become quite silly, and that is what the adapters of this stage play all understood. The McGuffin in this plot — Hitchcock's term for the object or idea that is central to the characters' motivations and the plot, but largely irrelevant for the audience — is a secret design for a silent airplane engine that is being traded by a shady group of spies, who are known as the 39 Steps.

Hannay, after having a mysterious woman, Annabella Schmidt (Maggie Mason), murdered in his apartment, heads off to the Scottish countryside in search of a certain house, stays over at a farmhouse where he encounters a woman who helps him (also Maggie Mason), encounters a shady professor named Jordan (Renee Rogoff), is disbelieved by the town sheriff after he's nearly killed (also Renee Rogoff), encounters another woman, Pamela (Maggie Mason) who ends up handcuffed to him, and more hilarity ensues as the two head back to London to figure out how to finally clear Hannay's name and foil the spies' plot.

Pamela (Maggie Mason) and Richard Hannay (Phil Wong) find shelter from Mr. and Mrs. McGarrigle (l to r: Greg Ayers and Renee Rogoff) in "The 39 Steps," presented by San Francisco Playhouse March 7 - April 20. Photo by Jessica Palopoli

All of this is done with a whole lot of wigs, hats, fake beards, and costume changes, and the true delights of the show come in the ingenuity of all that clownery. The fourth member of the cast, Greg Ayers, is a wildly talented clown and comedian — and both he and Rogoff are listed in the cast as "Clown," each responsible for dozens of characters.

One of the more memorable sequences comes in the first half, where all four actors recreate a train sequence with just the use of a few trunks for seats — Rogoff and Ayers playing both traveling salesmen who share a train compartment with Hannay, and police officers on the hunt for Hannay. Through movement and mime, and with the help of sound effects and lighting, the actors conjure the image of a rumbling train, and Hannay's escape out a window and onto the side of a bridge, which he scales before dropping into the water to swim away.

Director Susi Damilano, who is one of the co-founders of SF Playhouse, guides these performers to pull off many feats of quick-change transformation and madcap clowning, with the help of fight and movement coordinator Chelsea Pace. And this is no standard show when it comes to the demands on the actors, the comedic timing necessary, and the frenetic pace.

All four performers deserve equal praise and get equal laughs throughout, and it is a true ensemble accomplishment. Any small hiccups in timing — or wig-changing — will likely be ironed out as the show's six-week run continues, but in a show like this, sometimes the imperfections are part of the joke.

The 39 Steps is a crowd-pleaser to be sure, but Hitchcock buffs better not go into it thinking the original can't be laughed at.

'The 39 Steps' plays through April 20 at SF Playhouse. Find tickets here.