The pair's appearance on the show comes after 'Idol' judges Katy Perry and Lionel Richie performed at the coronation concert Sunday.
Luke Bryan is joined by guest judges Ed Sheeran and Alanis Morissette.
Richie was one of the many performers to take the stage in celebration of Charles' newly minted role.
The legendary singer is set to perform at Charles' coronation concert on Sunday.
Both judges are set to perform at King Charles III's coronation concert.
Lionel Richie chats with ET after 'American Idol's live episode on Monday, airing on ABC.
Katy Perry chats with ET after 'American Idol's live episode on Monday, airing on ABC.
Perry and Richie will be in the U.K. to perform at the coronation concert.
The country star teased their replacements ahead of his Stagecoach gig.
'American Idol' airs on Sundays and Mondays on ABC.
Lionel Richie chats with ET after the live taping of 'American Idol,' airing Sundays and Mondays on ABC.
The singer also jokes with ET about her plans for the Met Gala.
The 'American Idol' judge opened up to ET on Monday about his daughter's new husband.
Sofia Richie and Elliot Grainge tied the knot in France over the weekend.
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