Jon Hamm as Don Draper, Jessica Pare as Megan Draper, Charlie Hofheimer as Abe Drexler and Elisabeth Moss as Peggy Olson in the first episode of the show’s fifth season. (AMC)

After 18 months of waiting, an average of 3.5 million people tuned in Sunday to watch “Mad Men’s” fifth-season debut.

That’s a series best for the show — and about 600,000 more people than watched the fourth-season debut in July 2010. “Mad Men” had been off the air since October 2010, following the fourth-season finale, as the studio, the network and the creator wrangled over this and that — product placement within the show, adding another ad break, creator’s salary, blah, blah, blah.

The 3.5 million who tuned in to welcome back the boys of Sterling Cooper Draper Pryce is 5.5 million fewer than the crowd that collected at AMC on March 18 for the season finale of the network’s monster hit/zombie drama “The Walking Dead.”

(After the 9 p.m. season opener, AMC immediately replayed it at 11; the two telecasts totaled 4.4 million viewers, AMC said.)

While the public regarded “Mad Men” as but one of many entertainment choices Sunday night — “Desperate Housewives,” for instance, attracted 8.7 million viewers, and “The Good Wife” drew 9.3 million — the media’s hyperventilation over “Mad Men’s” return goes down as one of the most convincing demonstrations of mass hysteria since “The War of the Worlds,” the 1930s Orson Welles radio broadcast that sent much of the nation into a panic.

In the days leading up to, and in the immediate aftermath of, the series’s return, The Washington Post contributed:

●A report on: What if “Mad Men” took place in 2012?

●A photo gallery on: Who are today’s “Mad Men”?

●A preparatory guide to the “Mad Men” season debut

A review of the “Mad Men” season debut

A recap of the “Mad Men” season debut

And on, and on — 22 separate pieces and counting at press time, including this ratings column.

But The Post did not stand alone in this orgy of excess. One Reporter Who Covers Television (who apparently has a sense of shame), the L.A. Times’ Joe Flint, tweeted Monday when the numbers came in: “ ‘Mad Men’ draws 3.5 million viewers. I didn’t know NYT’s staff was that big.”

Kimmel to host Emmys

ABC late-night star Jimmy Kimmel will host ABC’s coverage of the 2012 Emmy Awards, the TV academy announced Monday.

It’s about time!

Previous hosts have included “Glee” star Jane Lynch, NBC late-night headliner Jimmy Fallon and Neil Patrick “I Can Host Anything” Harris. Yet somehow, Kimmel has not yet hosted the TV trophy show, which ABC takes turns broadcasting with NBC, CBS and Fox.

Apparently, it took a bunch of White House correspondents to convince Hollywood that Kimmel’s got what it takes to host a big-ticket event. Kimmel is hosting next month’s White House Correspondents’ Dinner.

That — and the fact that Kimmel recently stole ABC’s Academy Awards telecast with his annual post-Oscar special, in which his movie spoof, “Movie: The Movie,” pounded the movie spoof that opened the actual Oscar ceremony that night.

In fairness, Oscar host Billy Crystal and producer Brian Grazer hadn’t have a whole lot of time to put together their Oscar movie spoof — they stepped in after producer Brett Ratner stepped down and host Eddie Murphy followed suit with just weeks to go before the trophy show.

On Monday morning, Kimmel joked to the Associated Press about his hosting duties: “I hope to be able to do for the Emmys this year what Eddie Murphy did for the Oscars.”

Anyway, “Movie: The Movie” — which starred Meryl Streep, George Clooney, Tom Hanks, Martin Scorsese, Helen Mirren, Charlize Theron, Emily Blunt, J.J. Abrams, Tyler Perry, Samuel L. Jackson and a boatload of others — went viral. It was seen by more than 10 million viewers on Oscar night and has since garnered nearly 15 million views on YouTube — and who knows how many more on and Seriously, ABC didn’t know as of late last week that “Movie: The Movie” had opened on nearly 6,000 movie theaters nationwide and would run through April 26.

Getting back to ABC and why it’s taken so long to give Kimmel the Emmy hosting gig:

Last time ABC had the Emmy broadcast was in 2008 — the year it was hosted by a committee of reality-series hosts, including Tom Bergeron, Heidi Klum, Howie Mandel, Jeff Probst and Ryan Seacrest. And they’ll be remembered for having cleverly decided to toss out their prepared opening material and to wing it — just like they do on their reality shows!

The next morning, ABC execs flung themselves on casting couches and chewed the cushions in an ecstasy of grief — the trophy show had attracted the franchise’s smallest audience in its history: a mere 12 million viewers.

According to Probst, they were getting e-mails from Kimmel as they were dying onstage, saying: “You guys — try this! Here’s a couple of lines.”

“He gave us jokes, he tried everything to save us,” Probst told Seacrest the next morning on Seacrest’s syndicated radio show.

“I don’t know if it helped or not,” Probst added. “I couldn’t watch it this morning when I got up.”