Richard, an inaugural member of the Rock 'n' Roll Hall of Fame whose trademark howl of "Wooooo" can currently be heard in an instant-classic GEICO commercial, joins what has become a cast of characters for the show bearing some serious star wattage.
"I'm really thrilled," Cowell tells the latest edition of TV Guide about the new judge. "We're very happy."
The "American Idol" lookalike show (debuting Aug. 29) pairs celebrities with singers and pits the teams against one another.
Contestants who have already signed on include "Xena" star Lucy Lawless, Cheech Marin, Lea Thompson and Bronx native Alfonso Ribeiro.
On the show, they'll be paired with singers Clint Black, Macy Gray, Peter Frampton, Wynonna Judd, Patti LaBelle, Aaron Neville and Smokey Robinson.