New American Idol judge Jennifer Lopez has dazzled in a silver jumpsuit and vowed never to make cruel remarks to an aspiring singer.
Steven Tyler said his Aerosmith bandmates were jealous when they first learned he would join the judge's panel on the most-watched TV show in the US.
While the show's producers acknowledged British judge Simon Cowell was "irreplaceable" they said the show should be about the singers.
"Season 10 is like the remix. It is like a new beginning for what Idol is. These two are so talented...I think it worked out the best it ever could," music producer Randy Jackson, the only remaining original judge on the three-person panel, told a news conference.
The hiring of Tyler (62), and Lopez (41), as the two new judges marked an injection of glamour and hard rock star power to the 10-year-old show.
But asked who will take British judge Cowell's place as the "villain" on the new panel, both superstars looked blank.
"I believe in tough love, but I don't think I will ever, as an artist myself, be cruel to another artist. I think there are definitely better ways to say things," Jen said.
"It's not about role playing," said producer Nigel Lythgoe. "It is about being themselves."
He also dismissed reports that Lopez made "diva demands" over her Idol contract.
Both Lopez and Tyler are joining the show after recent career setbacks. Jen's last movie, The Back-Up Plan, flopped at the box office and Tyler had a second spell in rehab for prescription drug addiction a year ago.