Watch King Charles, Queen Camilla Visit ‘American Idol’: Video

It’s a British invasion! King Charles III and Queen Camilla appeared on American Idol after Katy Perry and Lionel Richie played at the coronation concert on Sunday, May 7.

During ABC’s broadcast of the competition series, guest judges Alanis Morrisette and Ed Sheeran filled in for Perry, 38, and Richie, 73. However, Idol checked in with the duo via satellite.

“What a party, what a party. It was unbelievable,” the “All Night Long” singer said.

“It was incredible,” Perry chimed in.

Richie that they were hoping to give Idol viewers a surprise. “Now we were trying to figure out what can we do to bring something different to the show. So, I would like to — Katy, excuse me, I have a surprise,” he said.

Perry moved to the side so Charles, 74, and Camilla, 75, could stand between them.

“Are you planning to do this all night long?” the king quipped, referring to Richie’s famous song. “I just wanted to check how long you’ll be using this room for.”

The “Hello” crooner laughed, “We have to give the room up right away!”

The monarch turned sincere as he praised their performances at Windsor Castle earlier that day. “Thank you so much for your brilliant performance. And Katy, it was wonderful. It really was,” Charles gushed.

“You were fantastic, absolutely fantastic,” Camilla added.

The performers said the regents were hosting a festive get-together as coronation weekend came to a close.

“We understand there’s a party,” Richie said.

“Ah, you’ve heard about that, have you?” Charles remarked, cheekily adding, “You’re busy with all these other things.”

The Alabama native assured him, “As soon as we finish, we’re coming to the party.”

“Well, you deserve it, bless you,” the king said. “Thank you both so much. It was a great treat.”

Charles wasn’t the only one to make a joke referring to Richie’s hit track, “All Night Long.” Earlier on Sunday, Prince William took the stage to pay tribute to his father. “I want to say a few words about my father and why I believe this weekend is so important,” the Prince of Wales, 40, said. “But don’t worry, unlike Lionel, I won’t go on all night long.”

Both his father as well as wife Princess Kate chuckled in the audience at Windsor Castle.

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The concert — which included performances from Nicole Scherzinger, Olly Murs and Take That — came one day after the coronation ceremony at Westminster Abbey. Both Perry and Lionel attended the big event, with the “Firework” singer even making headlines as she searched for her seat and nearly tripped.