Cowell, Randy Jackson, Kara DioGuardi (KEHR'-uh dee-oh-GWAR'-dee) and various guest judges kicked off the ninth season of the Fox singing competition last month. DeGeneres begins her stint Tuesday night.
In a video posted on the show's Web site, DeGeneres says Cowell is "actually meaner than I thought. It's hard to listen to him tell people things and for me not to go, `You poor thing!"'
Cowell has announced that he's leaving "Idol" after this season. Paula Abdul left over a salary dispute.
DeGeneres says no one has given her advice on judging - "they're just letting me do what I want to do."
