Luke Bryan Dishes on 'American Idol' Judges Filling for Coronation-Bound Katy Perry and Lionel Richie

American Idol will need fill-in judges soon after Katy Perry and Lionel Richie were both invited to perform at King Charles III's coronation concert on Sunday, May 7. ABC has not announced which big names will join the show temporarily, but Luke Bryan assured fans they will be "big-time" stars. Bryan was the only member of the judges' panel not invited to the U.K.

"It's big time. It's big time," the country star told Entertainment Tonight on April 28 before his headlining performance at the Stagecoach festival in Indio, California. "The people that we have filling in, contestants have used their songs many, many times. A lot more than mine!"

Bryan could not share more details because he wants to keep his Idol job. ABC is scheduled to air a live Idol episode the same day as the coronation concert, it seems physically impossible for Perry and Richie to get to Los Angeles in time for filming. Perry jokingly told ET last week that a hologram could replace them.

"You'll just have to tune in and wait and see. The hologram is finally real," she joked. She also suggested that Zooey Deschanel could go to the Met Gala on Monday in her place because they look alike. "I'm sending Zooey Deschanel in my place. Hi, Zoe. I love you," Perry said.

Although Perry and Richie are not U.K. residents, they have links to King Charles through their charitable work. Richie was the first Global Ambassador for the Prince's Trust, while Perry was an ambassador for the British Asian Trust and worked with UNICEF. Andrea Bocelli and Take That are also performing at the concert at Windsor Castle, hosted by Hugh Bonneville.

"I'm grateful I get to go. I met His Majesty-to-be a few years ago and he named me as one of the ambassadors to his organization, The British Asian Trust, which is an organization that helps fight to end child trafficking," Perry told ET. "So I'm also an ambassador for UNICEF, and it really aligned with my values. That's mostly why I'm going, to be an ambassador and to say, 'Hey, this is me from the USA.' No, but it's so cool."

Richie told ET he was "blown away" by the opportunity to perform at the U.K.'s first coronation in 70 years. "To be in this part of history, I'm just blown away, I'm so excited to be there," the music legend said. "I'm walking in history."

American Idol airs on ABC Sundays and Mondays at 8 p.m. ET. The show is also available to stream on Hulu.