Some of us first encountered Pee-wee Herman, actor Paul Reubens’s bizarre sketch character, way back in 1981, when HBO taped a low-budget, live stage show about the curious boy-man (man-boy?). He was outfitted in an ill-fitting Glen-plaid suit, white loafers and a red bow tie, and possessed a fiendish giggle and a squinty-eyed knack for sarcastic double-entendres.

Pee-wee’s superstardom grew through the ’80s to include two feature films and a much-loved Saturday-morning TV show that pioneered the Pixar-age belief that something made for children could in fact be meant for adults.

Then there was an unfortunate, career-snuffing end for Pee-wee, when Reubens was arrested for indecent exposure at a Florida porn theater in 1991. To think about that saga now causes a cringe: Was our media machine really that morally uptight? (Also: Was there really a time when people left their houses to watch porn?) The brouhaha seems even longer ago than Pee-wee’s brief heyday.

That’s all in the past, but as HBO’s sentimental “The Pee-wee Herman Show on Broadway” (airing Saturday night) clearly demonstrates, time has also passed our pal Pee-wee by. Though this marvelously staged production was tolerantly appreciated by critics during its successful run at the Stephen Sondheim Theatre late last year, “The Pee-wee Herman Show” suffers from a disappointing inability to harness its character’s original zip.

It’s not that Pee-wee isn’t loved; the audience seen here screams with rapt joy whenever anyone says the day’s secret word. Pee-wee’s long-anticipated return has been greeted fanatically. He is on the receiving end of much media-hipster worship, a love best exemplified by his recent appearance in one of those viral Andy Samberg videos for “Saturday Night Live.”

The letdown gets to something more elusive. For all the waiting, it turns out Pee-wee has nothing left to say, beyond “I know you are, but what am I?”

Well, what is he?

To Pee-wee we must at least partially credit the mainstream culture’s decades-long appreciation for mid-century American kitsch, in all its glitter, cereal-box dinosaurs, princess phones and sci-fi robots. The owners of funky tchotchke stores in any town’s gay/artsy neighborhood owe Pee-wee Herman (and the B-52s, and Godzilla) their undying gratitude for prolonging a fetish for retro junk culture that persists to this day.

Just like the original special, “The Pee-wee Herman Show on Broadway” treats us to a delightful interlude in which we are shown an old educational film from 1960, in which an elementary-school student named Phil learns good lunchroom manners and the importance of washing his hands, in order to avoid becoming a “Mr. Bungle.”

As these brush-cut young baby boomers shuffle to the sink and soap up, one is reminded of the sly novelty Pee-wee Herman first triggered, subverting the hide-under-the-school-desk-when-the-bomb-blows good citizenship of “Davy Crockett” and “Howdy Doody” reruns. Through a prism of satirical insouciance, Pee-wee gave us something to laugh at in all that ’50s kiddie-show conformity, which in some way helped suture the wounds of an angry, late-’60s counterculture.

Reubens, now 58, seems to have aged only slightly, which adds to Pee-wee’s creepy immortality. Nevertheless, the time machine meant to transport us back into a Pee-wee frame of mind has mysteriously broken down.

This shouldn’t be so surprising, since Pee-wee is no different from all those ’80s rock bands who set aside old hurts to reunite for a tour. Once onstage, all they must do is play the hits. Yet even when the crowd goes wild (as they do when Pee-wee performs his “Tequila” dance), some of the magic has plainly dissipated.

In Pee-wee’s case, getting the band back together includes corralling the panoply of anthropomorphic furniture and bric-a-brac living in his Playhouse, each of whom are given the sort of applause-line entrances once reserved for Lenny and Squiggy: There’s Chairy, Globey, Clocky, Magic Screen, Pterry the Pterodactyl, Randy the bully marionette, Jambi the genie and so on. Even the trio of falsetto-voiced geraniums in the windowsill are back in this lavish and lovingly restored set.

Old friends and neighbors (or reasonable facsimiles) are revived: the voluptuously beehived Miss Yvonne, the Jheri-curled Cowboy Curtis in his sheepskin chaps, a postal carrier, a King of Cartoons and an electrician named Sergio.

The latter has come to wire Pee-wee’s house for the Internet, a wasted plot point that briefly provides “The Pee-wee Herman Show’s” only glimmer of an intriguing concept: If Pee-wee gets online, will his innocence and anachronistic fantasy world be shattered? Also, it worries the toys: Does Windows render Magic Screen obsolete? Is GPS better than Globey? Is iTunes any replacement for Pee-wee’s dancing DJ robot, the stuttering Conky 3000?

Alas, these ideas — then vs. now, sarcasm vs. sincerity, ’50s manners vs. our maniacally modern indifference — remain firmly subliminal while “The Pee-wee Herman Show” devolves into the theatrical version of a clip job. Although it is 90 minutes long, it feels much longer, and the truly smart laughs are few — such as when Pee-wee shows off his abstinence ring, or when the mailman brings international postcards from Pee-wee’s pen pals: “Shalom, Pee-wee,” reads one. “My name is Shlomo! I’m 9 and I’ve been in the army two years already! If you want to know more about my country, just read the Bible!”

It difficult to tell whether Pee-wee (which is to say Reubens) is happy to be back. He seems more surly now, perhaps understandably so. A moment of joy comes when Pee-wee slowly, melodically lets the air squeal out of a balloon. It takes a full minute, but finally all the air escapes. It feels as though the same thing has happened to poor Pee-wee, too.

The Pee-wee Herman Show on Broadway

(90 minutes) airs at 10 p.m. Saturday on HBO.