Los Angeles, May 8 (IANS): Lionel Richie and Katy Perry weren't able to perform their normal tasks as judges on Sunday night's 'American Idol', as they were across the pond performing for the coronation of King Charles III, reports 'Variety'. So they brought back a souvenir for the show: The actual just-crowned King and Queen.

King Charles III and Queen Camilla were surprise guests on 'American Idol', in a pre-taped package introduced at the start of the show by host Ryan Seacrest, 'Variety' notes. The clip opens with Richie and Perry, in a room that appears to be inside Windsor Castle. Suddenly, in walks the King and Queen.

"I just wanted to check, how much, how long you'll be using this room for?" King Charles quipped to Richie, according to 'Variety'. Charles then thanked Richie for attending and performing at the coronation.

"Thank you so much for your brilliant performance and it was great," the monarch said.

"We understand there's a party," Richie said. "Oh, you've heard about that?" responded the King, who's known for his penchant for humour. Richie is said to have arranged the on-air cameo by the royals via his relationship with Charles, adds 'Variety'.

Alanis Morissette and Ed Sheeran filled in for Richie and Perry, joining Luke Bryan as 'American Idol' guest judges on May 7.

Perry, Richie, Take That and Andrea Bocelli were among the first acts confirmed for King Charles' coronation concert.

The singers were set to hit the stage at the May 7 concert on Windsor Castle grounds in front of 20,000 members of the public and invited guests. Also joining were Welsh bass-baritone Sir Bryn Terfel, singer-songwriter Freya Ridings and classical-soul composer-producer Alexis Ffrench.