LOS ANGELES — Last year, Prince. This year, Paul McCartney and Mariah Carey?

As "American Idol" starts singing again Tuesday, those connected with the Fox blockbuster acknowledge few limits when it comes to guest stars or ratings or product spinoffs. Or even rampant enthusiasm.

"This is the greatest music talent show ever," judge Randy Jackson asserted in a telephone news conference last week.

Fellow jurist Paula Abdul calls the show a "cultural phenomenon": "I get a kick out of the fact that there's not a day, not an hour, that goes by without someone talking about it, asking about it," she told The Associated Press.

Cecile Frot-Coutaz, who oversees "American Idol" as chief executive officer of producer FremantleMedia North America Inc., is more measured but no less upbeat about the upcoming season six, and beyond.

"I don't see anything that tells me that it's about to fall off the air," she said. "We won't be there for quite some time."

It's a defensible position regarding the No. 1 TV series.

Against expectations for an established series, "American Idol" has gained in the ratings, up 14 percent from 2005 (26.8 million average viewers) to 2006 (30.6 million). The finale with winner Taylor Hicks drew more than 36 million, according to Nielsen Media Research.

That topped the 2005 season-ender, in which Carrie Underwood claimed the title, and made it the third most-watched event of '06 after the Super Bowl and Academy Awards.

The most impressive number has a dollar sign in front of it — "American Idol" reportedly brings in $500 million a year in TV ad dollars. (Fox, a unit of News Corp., declined comment on the figure.)

Even impartial observers see blue skies directly ahead.

"There seems to be the same degree of fascination going into this season as there was last season," said analyst Bill Carroll of ad-buyer Katz Television. "It's sort of become the event of the year for viewers."

The series begins with a pair of two-hour episodes airing 8-10 p.m. EST Tuesday and Wednesday and featuring auditions in Minneapolis and Seattle. Details of a previously announced song-writing contest for the eventual winner's first single are pending, Frot-Coutaz said.

"American Idol," produced by FremantleMedia and 19 Entertainment, returns with a richer gloss than ever. Last year's finale included a surprise appearance by Prince, among the highest-profile guest stars and far removed from such golden oldie visitors as Rod Stewart.

"Prince blew the doors off. He is one of the quintessential ones of our time," Jackson said. Frot-Coutaz's take: "The fact we can get Prince is a real tribute to the show. ... (now) who knows who we can get?"

McCartney, an iconic figure who's an impressive "get" for any venture, is being courted and is rumored to be part of the new season. Carey may also end up on the guest list.

"Nothing's locked," Frot-Coutaz said of the ex-Beatle. "We've had discussions with him over the years. It's always a matter of making it work."