A Special Appearance by King Charles III and Queen Camilla on American Idol

The newly crowned King Charles III and Queen Camilla surprised viewers from the United Kingdom on Sunday night's premiere of American Idol together with judges Katy Perry and Lionel Richie.

Just hours after Perry and Richie both gave performances at the king's coronation concert at Windsor Castle, Charles and Camila made an unexpected cameo on the venerable singing competition series at the beginning of Sunday's episode.

The new monarchs greeted Perry and Richie and asked them in jest how long they intended to use the room while they streamed live from the castle for their speech.

Jokes aside, Perry and Richie were welcomed to the concert's afterparty as soon as they finished their Idol responsibilities, and Charles and Camilla complimented the singers for their "brilliant" performances.

Richie got Charles to get up during the coronation song with his singles "Easy (Like Sunday Morning)" and "All Night Long," and Perry inspired Princess Charlotte to sing along to "Roar" before making the entire audience feel like a "Firework." The judges found the coronation concert to be an entertaining one.

Perry talked to the media about the chance to take part in the celebrations before the special event. 

"I'm happy to be able to go. In a statement to the media last month, Perry said, "I met His Majesty-to-be a few years ago, and he named me as one of the ambassadors to his organisation, The British Asian Trust, which helps fight to eradicate child trafficking. 

I represent UNICEF as an ambassador because it actually reflects my ideals. I'm going primarily to serve as an ambassador and to introduce myself as a representative of the United States. It's so cool anyhow, she continued.

Richie, meanwhile, described the opportunity to perform for the king as "an honour."

The answer is undoubtedly, Richie told the media. "I mean, first of all, when you've been in the business for a long time, and, of course, when you get an invitation like this, the answer is absolutely," he said. "We've been friends for a very long time, and I've known him for a very long time, but to be asked is the whole thing."

While Richie and Perry go back from the UK, substitute judges Alanis Morissette and Ed Sheeran will preside over the competition. Additionally, Morissette is the Top 8's mentor.