DeGeneres added she'll have to "walk a fine line" in offering the contestants criticism in a "kind way."
"I'll be honest, but I don't really like to judge people. I like to opinionate in a necessary way," said DeGeneres.
"I've gone through the criticism, and I think a lot of these kids all of the sudden are just thrust into this limelight and don't understand that this is just the beginning of being judged. This is just the start of people having opinions about you, so hopefully I will be able to guide them through that and give them good advice and spot somebody that I think is going to be a huge talent that we'll watch just like everybody else that we've chosen through the years."
Fox announced on Wednesday that it had tapped DeGeneres to replace Paula Abdul -- who last month used her Twitter page to announce that she would not be returning as a judge for the show's ninth season. "I hope Paula is okay with it. I don't want anybody to think I took Paula's job away," explained DeGeneres.
"I feel like she was gone and then everybody was looking for somebody else, then I stepped in. I certainly don't want to be that person that is the evil taking Paula's job away."
DeGeneres said she was "shocked like everybody else" upon learning the news that Abdul would not be back.
"I thought Paula was a huge part of the show. I think that she's kind of part of the American Idol family. I was surprised," she said.
"I was sad, and so I went, 'Well that's going to be a hole that needs to be filled by somebody that really is going to contribute in a totally different way,' and had no idea -- didn't think about it for a second -- that it was going to be me."
DeGeneres said negotiations for her to join Idol's judging panel -- which seemed to be a bit of a surprise to Seacrest -- had "been going on for a few weeks, just quietly."
"I didn't know for sure if it was going to work out, and I kept wondering if you knew," she told Seacrest. "I thought you'd call me or talk to me or something. You knew that there was a possibility right?"
"These things always happen in a strange way, don't they?" replied Seacrest.
"I had a conversation a couple of weeks ago with one of the guys that runs Fox," he continued. "We talked about you in depth quite a bit. Then it went radio silence. Then yesterday I started getting these Blackberry messages and all of the subject lines were urgent. Of course it was all about the deal you had just closed, I assume within hours."
DeGeneres added that she did close the deal while taping Thursday's The Ellen DeGeneres Show episode on Wednesday.
"We had to tape out of order because we'd say, 'Yes, it's happening.' Then they'd all of a sudden say, 'No, wait. It's on hold.' I wanted to announce it in the second segment, so we jumped ahead," she explained.
"During the day they said, 'It seems we can announce it today. I said, 'Look, this is going to leak if we don't do this soon, we've got to get ahead of this thing.' I wanted to do it [Tuesday], and so it's just there's a lot of complicated things and moving parts that we had to align... At that point I was just going to announce it and go, 'Oops! I did it.'"
DeGeneres said she hopes to have a similar role on Idol's judging panel to the one Abdul vacated.
"I hope to be that compassionate person, because that's one thing that Paula did bring is that empathy and that compassion. I would like to think that I'll do that," she said.
"I love music, period. I've always loved music. And I'm a huge fan of the show. I haven't missed one show since Season 1. The people are the ones that choose the 'American Idol.' Ultimately it doesn't come down to some expert in the music industry, it comes down to everybody at home that says, 'That's the person I relate to, that's the person that I'm going to buy music from.'"
In addition, DeGeneres acknowledged that a So You Think You Can Dance guest judge appearance she made during a July broadcast of the series "started people talking" about her coming to Idol.
"They didn't even ask me to be a guest judge [on Idol]," said DeGeneres, explaining she was always looked at as a full-time replacement for Abdul.
"I had no idea that this was even a possibility when they came to me. I was like, 'Oh my god, are you kidding me? I love that show! I would absolutely give anything to be a part of that.'"
While Seacrest agreed with DeGeneres that it was "sad" to lose Abdul since she had been with Idol since the beginning, he welcomed DeGeneres with open arms.
"You're loved by so many people in this country, and I'm excited to embrace it and excited to have fun with you," he said. "It's going to add something totally different to a show that's been on for a long time."
Since DeGeneres plans to continue hosting her The Ellen DeGeneres Show daytime talk show while also judging Idol, Seacrest asked her how she'll manage to juggle both jobs.
After heckling Seacrest about asking her that question given his own multiple commitments, she said her schedule will have to be adjusted "a little bit" when both shows are airing at the same time.
"For those days we're going to shoot [The Ellen DeGeneres Show] earlier, and then I'm going to jump in my car and I'm going to drive over and sit down and be entertained by these kids singing for us," she explained. "I'm not worried about that."
The Ellen DeGeneres Show is currently in its seventh season, and she thinks that her new role as an Idol judge will help her talk show.
"It'll add a whole lot of content to my show and I think I'm going to bring something to that show that's fresh I hope. I'm going to do it like I do everything else I enter into, with 110% of all I got," said DeGeneres, who also noted that -- given her position as a daytime talk show host -- will be a slightly different position than Cowell, Randy Jackson and Kara DioGuardi.
"I'm, unfortunately, going to have to have [eliminated contestants] on my show the next day. No other judge up there can say mean things and then have to have them on their show the next day."
Since a big part of being an Idol judge is the ability to banter with Seacrest -- something Cowell has mastered in recent years -- DeGeneres gave Idol viewers a taste of what it will be like during her interview.
"We get to see each other now too because we never saw each other anymore," DeGeneres told Seacrest.
"We've tried to actually hang out in the last six months and now apparently we'll be hanging Tuesdays and Wednesdays," he answered.
"Well, three days for the first three weeks, right?" she asked.
"You know better than I," said Seacrest.
"Yes, because there's a boys night, girls night, results night," she said, a reference to the semifinal rounds at the beginning of each Idol season.
"See, you've actually gone through the schedule," replied Seacrest. "We don't even think about it until it's January."
While it has reportedly yet to be decided if she'll participate in the pre-taped "Hollywood Week," which is scheduled to film late this year, DeGeneres said she's eager to meet her new Idol colleagues.
"I haven't even talked to Randy or Kara or Simon," she said. "But this is going to be a whole lot of fun."
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