While Simon Cowell and Ellen DeGeneres haven’t had a lot of time to spend together since DeGeneres signed on as the newest American Idol judge last September — he’s been in London shooting The X-Factor, while she’s been in LA working on her Emmy-winning talk show — the duo have no problem being honest with each other about their relationship as soon-to-be coworkers.

“Simon really is, in my opinion, mean to people sometimes,” says DeGeneres, who makes her first appearance on Idol when Hollywood Week kicks off on Feb. 9. “So I think I’ll be hard [as a judge], but if he’s rude, I’m going to let him know he’s rude.”

“And I may disagree with you,” Cowell retorts. “If everything is ‘After you,’ ‘No, after you,’ that’s uncomfortable.”

In their first interview together, daytime’s talk show sweetheart and TV’s grumpiest star tackle everything from seating arrangements at the judges’ table (“I think I’m on Simon’s lap,” jokes DeGeneres) to theme nights they’d like to see (“I’d like something with a bit more emotion. Something like Why I Hate You So Much,” says Cowell). As for rumors that Cowell might leave the show after his contract is up in 2010, DeGeneres is not going to let her new co-star escape without a fight. “If Simon goes, I go!” declares DeGeneres, prompting Cowell to laugh — and squirm a bit. “Oh, Ellen!… That’s quite a tricky situation you’ve put me into! I think right now we have to concentrate on the next season and just get through that and worry about everything else afterwards.”

For more with Simon and Ellen — including what the openly gay talk show host thinks of Cowell’s infamous gay-themed banter with Idol host Ryan Seacrest — as well as a winter TV preview featuring the scoop on 25 new and returning shows, pick up the new issue of Entertainment Weekly, on stands January 8.