Nicki Minaj (Jordan Strauss/JORDAN STRAUSS/INVISION/AP)

Ironically, Jackson, who’s been one of the judges on the show since its premiere in the summer of ’02, turned out to be the biggest surprise; he’d been written off when the network began taking steps to shake up the country’s most popular non-football TV show, after it wound up its 11th edition with its smallest finale audience ever.

Jackson had been expected to stick in some “mentoring” capacity — he did, after all, play a big role in snagging Mariah Carey as one of the upcoming season’s new judges, in his capacity as her co-manager.

Keith Urban (Josh Sisk/FTWP)

His colleagues of the past two seasons, Steven Tyler and Jennifer Lopez announced in July they were bowing out, shortly before Fox announced Carey had been signed but declined to confirm the reported $18 million paycheck.

Fox and the “Idol” producers are under pressure to keep the show fresh, as two other, newer singing competition series — NBC’s “The Voice” and Simon Cowell’s “X Factor” — saturate the TV landscape in the fall, leaving fans of the genre sated before “Idol” starts its 12th edition in January.

Not long after last season’s low-rated “Idol” finale, culminating in the inevitable crowning of the Cute Scruffy White Guy with Guitar (Phil Phillips), was the least watched in the franchise’s history, Fox Entertainment chief Kevin Reilly told TV critics there would be a show shakeup.

“Not being the only game in town now, we need to keep things fresh,” Reilly said.

“Keeping things fresh” has come to mean whacking the judge panel on these singing competition shows, which these days all about the judges and their antics, with singers being relegated to the role of props and bit players, complain TV and music critics alike.

“With an unparalleled star like Mariah, fan-favorite Randy, chart-toppers like Nicki and Keith and our incomparable host Ryan, we’ve put together one of the most exciting judging panels around,” Fox alternative programming chief Mike Darnell boasted in Sunday’s announcement.

Minaj and Urban’s name rose to the top in the last few weeks, from a pile of possibles that included Miley Cyrus, Kanye West, Nick Jonas, Adam Lambert, Katy Perry, Brad Paisley, and more.

“Nicki is someone who represents a different side of the music industry, who has now crossed into mainstream culture with her unique artistry, style and flair. Keith is one of country music’s true stars who brings with him charm, wit and knowledge about the industry,” Cecile Frot-Coutaz, the CEO of “Idol”-producing FremantleMedia, by way of explaining the new judges.

Randy Jackson (David Livingston/GETTY IMAGES)

Pop stars Britney Spears and Demi Lovato replaced judges Paula Abdul and Nicole Scherzinger for last week’s return of Fox’s “The X Factor” — part of a shakeup promised by show creator Simon Cowell after that show’s first season attracted far fewer viewers than he and Fox had promised. Wednesday’s second-season debut opened Wednesday with 4 million fewer viewers than Season 1’s disappointing kickoff, and the next night “X” lost a few million viewers more.

Spears is being paid $15 million for her services on the show, according to reports.

The selection of Minaj, known for her iridescent wigs and goofy outfits, should not have come as much of a surprise to fans, she having performed on “Idol” last season and told JLo to scoot over to give her a shot at guest judging the show. Lopez replied frostily that there was not enough room.

Minaj auditioned anyway. The glam/pop/hiphop/etc. singer, who’d tastefully staged her own exorcism and levitation to heaven, after singing a number in a torture rack, at the Grammy Awards/Whitney Houston memorial in February, performed “Starships” on “Idol” that night.

But all eyes were on her costume as she worked the stage, alternately appearing to lip-synch and live synch. And the American Idol Decency Police congealed in their seats when Minaj suddenly turned her back to the audience and stuffed a rogue breast back into the little strips that served as the bodice of the dress she was very nearly wearing.

“There were parts of that performance that were a little high-risk, if you know what I’m saying,” show host Ryan Seacrest giggled nervously when she finished.

“I know,” Minaj responded wittily. And a new “Idol” star was born.

Urban, on the other hand, comes with singing competition judging experience, having done so on the recent Australian edition of “The Voice.” Late last week, Urban announced he was exiting his gig as a mentor/judge on that show, after just one season, clearing the way to join “American Idol.”

“As much as I’d love to do it again, it’s clear that the recording and promoting of a new album, a tour and other commitments, will keep me from being a part of the second season,” he explained as he stepped down from “The Voice.”

Mariah Carey (Arnold Turner/INVISION FOR BMI)

Fox finally made the announcement Sunday morning, because the judges’ round of auditions for the new seasons was scheduled to begin later that day in New York.

Fox’s Sunday’s announcement comes days after Disney sent a clip to reporters of last Friday’s “Katie” episode in which she asked JLo for her reaction to the addition of Minaj and Urban to the show and the return of Jackson, which Katie assured JLo, had been confirmed. Fox jumped all over that and said in a statement “the only confirmed judge for ‘American Idol’ is Mariah Carey. No other judges have been announced at this time.”