Now that Simon Cowell has made public his plans to leave “American Idol,” the show that made him a household name in the U.S., he’s becoming even more of a high-maintenance diva than before. One person who isn’t appreciating his on-set antics is Ellen Degeneres, the show’s new judge. Ellen has made a lot of schedule re-arrangements with her daytime talk show to join the show and isn’t happy when Simon is hours late for taping. Who could blame her? Sources also say that Cowell’s relationship with the show’s co-creator and exec producer Simon Fuller is also strained. The reason: the two men are in a heated tug-of-war over legendary music producer and Sony Music CEO Tommy Mottola. Fuller wants Mottola to replace Simon Cowell on Idol, but Cowell wants the industry giant as a judge on his new version of “X Factor.” Cage match alert!

EXCLUSIVE: It was American Idol’s newest judge Ellen DeGeneres’ first day of the 9th season’s taping of the Hollywood segment, and she was excited and nervous, sources tell us. But then that turned to anger. Because, our insiders say, Simon Cowell was an hour and a half late for the taping. And Ellen stewed while she waited. She had reason: to accomodate both her talk show hosting duties and her American Idol judging duties, she had moved up her schedule so that now she shot the talk show earlier in the day and then jumped in the car to go to Idol. She was on time, and Cowell was not. “Here it was the first day of taping of the Hollywood shows, and Ellen was there waiting for Simon to show up. Ellen’s new to the gig and she’s very organized and she made a commitment to take this on, and now she’s asking herself, ‘What did I get myself into?’ She called Simon Cowell a prima donna. So right from the start, the chemistry isn’t great,” an insider tells us.

With that, Ellen Degeneres contacted the pal who brought her to the primetime hit show, Fox alternative programming chief Mike Darnell, and made a request: she asked him to “hurry up and pick” Simon’s successor. Cowell has told the world this will be his last season judging Idol to do his own U.S. version of The X Factor. But there’s a problem, a big multi-pronged one, and it involves Ellen vs Simon, and Simon Fuller vs Simon Cowell, and American Idol vs The X Factor as well.

Our sources say that American Idol’s first choice to succeed Cowell is former Sony music chief Tommy Mottola, best known to the public as Mariah Carey’s controlling ex-husband and the controversial boss of Michael Jackson and Michael George who presided not so much over their musical heydays but mostly their scandal-plagued aftermaths. But get this — Cowell has also designated Mottola as first choice to be a judge on Simon’s American X Factor just announced.

Cowell is reportedly being paid nearly $175 million for launching the new talent search show in the Fall of 2011. (Cowell didn’t own American Idol and only gets paid to appear on it, but he does own X Factor and the whole brand. It is currently shown in 17 countries worldwide and is the No. 1 TV entertainment format in Europe. The X Factor format is owned by Syco, a global music, television and film production joint venture between Cowell and Sony Music Entertainment.)

Execs behind American Idol and The X Factor want a high-profile music industry professional to give some gravitas. And our sources say Mottola, who hasn’t made headlines since he left Sony and started a new music label, is loving this situation. He’s in the middle of an American TV tug of war!

According to our insiders, Fox, Darnell, and Fremantle’s American Idol producers have “come up with a list of 25 people” led by the 60-year-old Tommy Mottola, co-owner of Casablanca Records in a joint venture with the Universal Music Group. He’s also been a guest on Idol. Viwers of the show know him as Mariah’s ex but also as the current husband of Mexican singer Thalía. True, he’s a music legend in his own right for heading up Sony Music Entertainment, parent of the Columbia label, for 15 years. But ever since leaving, he’s been on the downlow. “What’s he doing now? Good question. He’s got some label. But in truth he hasn’t done much,” one of our sources shrugged. Mottola also is known as a mentor and former talent manager. His most famous proteges were Hall & Oates, Carly Simon, John Mellencamp, Diana Ross, and Taylor Dayne as well as Mariah Carey in the 1990s, and Jessica Simpson and Jennifer Lopez in the early 2000s.

Cowell’s music background and blunt assessments anchor American Idol, “but he’s also a music industry insider and Mottola fits that bill. And he certainly knows how to find young talent,” our source explained. “Mottola is frontrunner for Idol, but when Simon became aware of this, he began trying to get Tommy to team with him and Paula Abdul for his new show The X Factor.” Our insider feel there is the very real likelihood that Paula Abdul will sign for big dough to reteam with Cowell.

Let’s not forget also there is real rivalry between The Two Simons: Simon Cowell and American Idol’s Simon Fuller. (See SHOW THEM THE MONEY: Is Simon Fuller’s Sweetened TV Deal Richer Than Cowell’s?) Cowell turned down $100 million to stay on Idol. But if he signs Abdul and starts his X Factor with two of the three original American Idol judges, this poses a real threat to Fuller. Especially since two of the original three Idol judges are gone, leaving only original judge Randy Jackson and last season’s new judge Kara DioGuardi — both well-known musicians and record producers — and this season’s new non-music-biz judge Ellen DeGeneres, who is 51 and receives a reported $5 million-a-year for the gig.

As for Ellen vs Simon, even before cameras rolled DeGeneres was marketing herself counter to Cowell. “I think he’s mean and I think he says things in an insensitive way and I don’t think that’s the way to get a point across,” she told one interviewer. “I’m going to be brutally honest, in a kind way.” But even then, as one newspaper noted, “the chemistry between these two stars will be a key plotline.” Still, Fox and the show’s suits are handling her with kid gloves because of the cross-promotion benefits expected between Idol and her successful talk show. (DeGeneres has said repeatedly that she plans to book Idol contestants the day after they’re booted.) So, like her or not, and a lot of fans have voiced their disapproval, she is the show’s future, and Cowell is its past.

“Mottola is in the middle of all that and beneficiary of it. Mottola has remarkable leverage because of this tug of war and will get a big payday from somebody,” our source predicted.

[From Deadline Hollywood]

Things sure have a way of getting ugly when huge amounts of money are involved, eh? As for Simon vs. Ellen, I think it may be overblown, but given Ellen’s tight schedule on both shows, the least Simon could do is show up on time and respect her. The interview I read with both of them in Entertainment Weekly seemed very friendly – Ellen even said her goal was to get Simon to dance by the end of the season. Of course, things can be completely different behind the closed doors of a TV set, right? Either way, Simon seems like he can’t wait to get the hell off “Idol,” but that doesn’t mean “X Factor” is a guaranteed hit. He might want to think twice about burning bridges with Fuller and with Fox!

EW cover courtesy of CoverAwards.