WHAT IT’S ABOUT The 46th season of “Sesame Street” will air on HBO, in 30-minute editions, down from the traditional PBS hour. The set has been spruced up, while there are some new segments, and new cast member, Nina (Suki Lopez) who works at the laundromat and bike store.

Some other changes: Elmo’s moved into 123; Abby has a nice garden; Big Bird has a new nest in a tree; Oscar still has his can, but now also an adjoining recycling bin. And yes, it’s all still produced by Sesame Workshop out of the Kaufman Astoria Studios.

MY SAY “Sesame Street” and “Saturday Night Live” are the totemic shows of the New York production world, so just imagine the uproar if, say, “SNL” were to jump to Showtime. (Oh, and by the way, it wouldn’t be “live” anymore, either. Sorry . . . But the good news — no more commercials!)

You may be wondering when the roar will be coming up over “Street’s” decampment to HBO. Announced over the summer, there were some initial gasps, a flurry of “what’s?!,” then . . . silence. We move fast these days. No time to ponder historic shifts. Too much else going on.

But this is a historic shift and — when specifically embracing the broad scope of TV history — an ironic one, too. Joan Ganz Cooney procured $8 million from various sources in the late ’60s to launch “Street,” which debuted Nov. 10, 1969. Cookie Monster messed up Kermit’s lecture on the letter “W.” (Remember?) Carol Burnett was the first celebrity guest. Not much has changed since then and — of course — everything else has changed, most notably the TV ecosystem. Something called “cable TV” was beginning to stir back then and something else called “Home Box Office” launched on Nov. 8, 1972. Through all those years, and the ones since, the letter “W” — along with all the other letters — have had their close-ups countless times. Cookie Monster is, was, and always will be, a cookie monster.

But Cooney’s idea was radical for the time — a heady fusion of social, educational and commercial goals designed to remediate the woeful state of kids’ TV circa 1969. If kids — especially poor kids, aged 3-5, in inner cities — spent hundreds of hours in front of the set, then fight the fire with more fire. “Street” was always fast — a pastiche of clips, songs and animation, some of which were designed to mimic commercials. HBO’s version is likewise, except now in half-hour form, which is almost certainly a concession to costs (and HBO’s version does look expensive).

Speaking of expensive, you’ve doubtless already heard that the Street itself has gone upscale, too. But it was never exactly downscale either: HBO’s Sesame Street does seem a little more colorful. The floral arrangements are certainly pricey.

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There are lots of other small touches — or technical flourishes — along with new cast members, notably Nina. Otherwise, best of luck finding anything radically different because there isn’t all that much that’s changed.

So the irony, and possibly a cruel one? That a show expressly created for the underprivileged and over-TV-exposed now airs on the world’s richest cable channel.

Nevertheless, the sting of that seems eased by Sesame Workshop’s new arrangement with PBS: These episodes will air on public TV nine months from now. (HBO will air a total of 35; PBS is currently airing repeats.) While we may move fast, preschool kids don’t move quite as fast. Most won’t even know — or care — the episodes are nine months old when they finally see them on free TV.

BOTTOM LINE Instead of an "irony," maybe this is a “win-win” — for HBO, public TV, an iconic series and those kids.