For those of you wondering what NBC was doing when it put its new ’60s-set drama “Playboy Club” into the intense Monday-at-10 competition, we have an answer!

The season’s first cancellation.

NBC has bounced the bunnies from its Monday slate because the network thinks it can do better with anchor Brian Williams.

NBC apparently believes that on Halloween night, millions of adults who’ve been fending off mobs of sugared-up kids will be too exhausted by 10 to contemplate another glutinous episode of ABC’s “Castle” or CBS’s “Hawaii Five-O.” So NBC will unveil . . . Brian Williams, headlining a new newsmag that’s bizarrely named “Rock Center With Brian Williams.”

Meredith Vieira, Harry Smith, Kate Snow, Matt Lauer and Ann Curry are among those lined up to contribute to “Rock Center,” which obviously is a reference to the famous Manhattan complex where NBC is based — which is still not a good enough reason to saddle Brian’s new show with that name. We’re guessing that either NBC could not clear “Rockefeller Center” or that “Rockefeller” skewed really old — and, of course, “30 Rock” is already taken.

In “Playboy Club’s” time slot until Halloween night, you’ll see reruns of NBC’s overhaul of Helen Mirren’s crime drama “Prime Suspect.”

“Rock Center” will air in the hour until the Feb. 6 premiere of “Smash” — NBC’s much-ballyhooed “Glee”-for-adults drama about the production of a Broadway musical based on Marilyn Monroe’s life. “Smash” will star Debra Messing and “American Idol” non-winner Katharine McPhee.

“Playboy Club” never really stood a chance on NBC. Despite all the hoopla that preceded its Premiere Week unveiling — including much chest-thumping by conservatives and Gloria Steinem, all mother’s milk for network marketing suits — the first episode attracted just 5 million viewers.

That opening audience would have been hailed as historic had the “homage” to the ’60s-set “Mad Men” aired on “Mad Men’s” network, AMC. Alas, 5 million viewers was not a large-enough audience to sustain a broadcast-network series — particularly one that opened in third place in its time slot, in a three-way broadcast race, among the 18-to-49-year-old viewers whom advertisers target.

In its second week, “Playboy Club” clocked an even more disappointing 4 million viewers — laps behind time-slot competish “Castle” (11.7 million viewers) and “Hawaii Five-O” (11.3 million).

On Monday, “Castle” and “Hawaii Five-O” finally drove the bunnies off, when “Playboy” logged an anorexic 3.4 million viewers and was once again an also-ran among 18-to-49-year-olds.

‘Whitney’ gets full season

In happier NBC news: The network has given full-season pickups to two new comedy series: “Whitney” and “Up All Night.” According to NBC Entertainment Chairman Robert Greenblatt: “We made comedy an important goal” and network execs are “thrilled with the creative direction of both shows, as well as the potential for them to continue to build loyal audiences in the coming months.”

And yet, “Up All Night” averaged about 5 million viewers last week and finished fourth in its Wednesday-at-8 time slot among 18-to-49-year-olds. Sound familiar?

Ditto “Whitney,” on Thursday nights at 9:30.

Now, about those two new chick-coms:

“Up All Night” is executive-produced by “Saturday Night Live” impresario Lorne Michaels (Christina Applegate, Will Arnett and Maya Rudolph star).

“Whitney” — a rare multi-cam laugh-tracked sitcom on NBC’s lineup — stars Whitney Cummings and Chris D’Elia. Cummings is also one of the executive producers.

Misunderstood Simon

Simon Cowell, the once-mighty lion king of reality TV, now says that when he cockily told a trade publication that any audience less than 20 million strong for his new singing competition, “The X Factor,” would be a “disappointment,” it was all a “misunderstanding.”

After two weeks of considerably short-of-20 million viewers for his new Fox series, Cowell took to the celebrity suck-up show “Access Hollywood” to explain: “That was a slight misunderstanding.”

“I wasn’t saying I want 20 million for the first episode. I was saying we want to hit 20 million,” Simon said.

The downside of that swaggering 20-million-or-die pose he took with the Hollywood Reporter back before “The X Factor” debuted, he says he now realizes, is that “anything now under 20 million is a disaster.”

Which perfectly describes the Cowell-created Fox press-wrangling department’s super-headache this fall season.

Sadly, it appears that Cowell has been neutered since he used to strut around the TV landscape while a judge on Fox’s other singing-competition series, “American Idol.” As owner of “The X Factor,” his behavior these days is more that of a cautious businessman.

“As much as people want you to succeed, there’s a ton of people that want you to fail,” Cowell complained to “Access” about the reporters who accurately reported “The X Factor’s” premiere and second-week ratings.

This is called “journalism” — which, in Cowell’s defense, is something TV celebrities are hardly ever exposed to.

“I took a bite in the neck that first day,” Cowell said in the interview — which is not, as you might think, the first time someone has actually bitten themselves in the neck in Hollywood.

In the interview, Simon did stick that same neck out so far as to predict that “The X Factor” will draw 20 million viewers — at some point.

It’s a safe bet; the finale probably will attract that many people.

“I do believe — in time, because I believe in the show — we’re going to hit those numbers,” he told the all-things-celebrity show, adding cautiously: “You’ve got to remember, this is a new show.”

Golly, we miss the old Simon!