It was an event 7 1/2 years in the making, so Mike Francesa and Chris Russo knew they would have a receptive audience Wednesday night when they took the stage at Radio City Music Hall for their reunion show.

“I think we could read the phone book and half these fans would get a kick out of it,” Russo said before the fundraiser for the Garden of Dreams Foundation that was shown on MSG Plus and heard on WFAN and SiriusXM Radio.

“We have a ready-made audience. I mean, I’m not doing this in front of Queen Elizabeth. From that standpoint, I think we’ll be OK.”

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The former longtime partners on WFAN’s “Mike and the Mad Dog” show certainly seemed to enjoy soaking in the atmosphere before the show began with them rising up to the stage to Russo’s familiar “Aaaaand” show open.

The show opened with a video greeting from New York Gov. Andrew Cuomo, then a video look back at the show’s history and legacy.

When Francesa and Russo rose up from beneath stage level, they received a standing ovation from the capacity crowd, which was multi-generational but predominantly male.

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Russo got in the first zinger, asking, “Has Matt Harvey gone to the bathroom yet?” From there the duo spent 15 minutes or so kibitzing about current and past events, displaying the chemistry that long was their trademark.

That certainly was so in the eyes of a spirited audience of true believers that adopted a raucous demeanor more commonly seen in sports stadiums than at the venerable theater.

Their first guest, Tom Coughlin, received a standing ovation.

Under some gentle prodding from Francesa, he acknowledged a bit of frustration seeing the Giants rebuild their defense this offseason with him no longer the head coach.

“It didn’t happen,” he said. “Now it’s happening.”

When Francesa asked whether Coughlin would have any involvement with the Giants this season, as president John Mara has suggested, he said, “I don’t think so.”

Coughlin wasn’t the only guest greeted with a standing ovation. Joe Torre, Mark Messier and Bobby Valentine were, too.

But one of the most raucous reactions came when free agent quarterback Ryan Fitzpatrick was shown on the video board and Russo shouted, “Sign the contract!”

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Fans joined in trying to encourage Fitzpatrick to re-sign with the Jets.

So attuned was the crowd to “Mike and the Mad Dog” traditions that a huge cheer arose when Francesa said he and Russo would be picking over/under victory totals for Major League Baseball teams.

Longtime WFAN update men John Minko and Bob Heussler received loud ovations when they were acknowledged from the stage.

The show tended to drag a bit during the interview segments and come alive when Francesa and Russo were interacting one-on-one.

When answering a question from a fan about whether they might reunite for a regularly scheduled show, Francesa said, “Never say never. How’s that?”

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Among their guests, either onstage for official interviews or in the audience, were the comedian Tracy Morgan, former New York-area managers and coaches Torre, Valentine, Coughlin and Jeff Van Gundy, and current and former athletes including Messier, Earl Monroe, Adam Graves, Larry Johnson, John Starks, Victor Cruz, Justin Tuck, Rod Gilbert and Gerry Cooney.

“You’re not nervous, but you want to make sure everything works out,” Francesa said before the show. “We’re a little apprehensive that everything works well, that’s all . . . There are a lot of bells and whistles to this.”

Francesa and Russo were chummy on the red carpet before the show, as they have been throughout the planning process. Barry Watkins, the Garden of Dreams chairman who had the original idea for the reunion, said, “The guys have been great. It’s been so smooth, the entire planning of it. They were fantastic together.”

Watkins said the goal was to raise $1 million for the foundation, which supports a variety of programs for young people in need, and going into the evening it already had raised $1.1 million. Viewers and listeners to the program were encouraged to donate more during the show.

Before attending a VIP reception, various guests paid tribute to the duo, which broke up in August 2008 after 19 years together.

The actor/comedian Michael Rappaport said, “They’re very New York, staples of New York — original, fun, feisty. They were trendsetters in the sports radio, banter thing. I’m having ’90s flashbacks. The ’90s are the new ’70s.”

Said Van Gundy: “For Mike and Chris to get back together for a night, I admire them a lot for whatever in the past happened that they said, hey, let’s do it for them and let’s do it for the underserved kids in the community, and I think it’s awesome.”

Valentine, the former Mets manager, joked, “I was always interested in what they were talking about — but it was less interesting when they were talking about me.”

Starks, the former Knick, said, “They made the game fun. They made it interesting, especially after you had a bad night.”