I’ll suggest one reason why Bill Irwin and David Shiner decided to call their show OLD HATS (now at The Pershing Square Signature Center).

The hats they use will get old very quickly from the enormous wear-and-tear that these two gifted farceurs impose on them.

For early in this two-hour slapstick-and-slapshtick romp, these two mimes have a competition to see who can better manipulate a hat. Each spins and rolls his chapeau onto his hands and arms, and then above his heads in a frenemy-filled anything-you-can-do-I-can-do-better battle. Their nerves get increasingly frayed, but probably not as much as the brims of the hats.

In this sequence, Irwin adopts a look on his face that has such seriousness of purpose that it almost could pass for a scowl. At a moment’s notice, however, he makes his face suddenly light up as if it’s been let out of prison and is now ready to savor the joys of the world.

The real wonder is his ability to stretch his head upwards from the bottom of his neck to what threatens to be giraffe-like proportions. With his bones seemingly replete with jelly-doughnut filling, Irwin moves so freely that he would have passed any Bob Fosse audition and become part of his dance ensemble.

Taking more of a straight-man role is Shiner, who’s always been the less showy and quirky of the two. And yet, his job is more difficult that it may seem. Just as Will Rogers enjoyed saying that veterinarians are more impressive than doctors because their patients can’t tell them what’s wrong, a straight-man who’s denied the use of his voice can’t set up matters as easily.

Even when the two play rival political candidates, they stay wordless. Here each is clad in the precise same suit, but Shiner has a blue tie to Irwin’s red. Because this no doubt is meant to represent Americans’ Democrat and Republican proclivities, we must wonder if the men flipped a coin to see who’d wear the red tie and who’d wear the blue. If they did — did Irwin lose the toss?

This nifty sketch shows how candidates can be popular with the populace at one moment and anathema the next. What theatergoers may well take away is a wish that all our current candidates could be equally silent. When the two opponents devolve to actually battering each other physically, we get the metaphor of what we’ve been seeing this entire electoral season.

So with the silence-is-golden maxim in effect, there’s no trash talk — although there is a good deal of searching through trash in one sketch. Another playlet suggests that we’d be better off without technology; another won’t please lovers of cats (the animals; not the musical, which comparatively few like, anyway.) Warning: stuffed animals WILL be harmed during this stage show.

One sketch spoofs magicians who aren’t nearly the equal of these two. Irwin plays a most loyal assistant who expresses constant awe, reacting as if every minor trick Shiner does is extraordinary. Oh, what a tangled web Shiner literally weaves during this sequence.

We’re also reminded of one truism of magic shows: tricks that don’t work are far more entertaining than ones that do. Many polls reveal that people come to the theater first and foremost to laugh, so stunts that fail get guffaws while maneuvers that succeed get polite applause.

For a show of this scope, there are pretty impressive production values, including backdrop after backdrop. When they’re changed behind the curtain, leather-jacketed lass Shaina Taub steps out of the shadows to sing her original songs backed by her wonderfully intense four-piece band. One of her lyrics — “Three cheers to the agony; a toast to the pain” – can well describe the physical rigors that both Irwin and Shiner endure.

Irwin can even play the ukulele, and that leads to a sequence where he and Shiner are so moved by the music that they start scatting. Just when you assume this will be the closest you’ll get to hearing actual words from the pair, out they come with a bit of a Rodgers and Hammerstein title song, a Shakespeare soliloquy, an Oscar-winning standard, an Oscar-winning film and even an absurdist drama.

But for the most part, the pair offers library-level silence. Irwin proves he doesn’t need dialogue when he portrays a waiter who has no respect for his restaurant’s spaghetti. Here he manages to look a little like Groucho and performs with the same sense of anarchy. It’s a bit of a change for him, for his usual persona has him think that he’s this real swinger when he couldn’t be more of a square.

Anyone who likes to sit in the first row at shows (and that means many of us) should be apprised that you may well find Irwin and/or Shiner suddenly in front of you ready to hug – or, perhaps more accurately, semi-assault you.

You also run the risk of being brought on stage. This certainly happens in Shiner’s sketch called “Cowboy Cinema.” Here he directs a film, and, as you may have inferred from the show’s paucity of language, it’s a silent movie. Thus anyone who decides to join him in trodding the boards had best pay rapt attention to his instructions which he only communicates through charades. If you can’t follow what he’s “saying” and what he wants you to do, you’ll be greeted with his exasperated look and feel mighty silly.

How audience members rise to the “Cowboy Cinema” challenge is part of the fun — even when they’re jostled to the point that would be considered sexual harassment on a subway. Certainly the unchosen theatergoers who are still in their seats admire them, for they react to their on-stage brethren with applause that says “If I’d been dragged up there, I only hope that I’d be as good.”

Of course, anyone who goes on stage will be most appreciated and enjoyed by the friends or relatives who came with them to see OLD HATS. Perhaps in this one instance, the taking of photographs and use of recording devices should NOT be strictly prohibited. Let the memory live again.