When Kate Middleton and Prince William tied the knot on April 29, 2011, millions of people around the world watched the Westminster Abbey ceremony. But following the public wedding, the couple threw two private receptions where the focus was on their personalities. Soon after the event, people found out that pop star Ellie Goulding had been the night’s musical entertainment, and she serenaded the couple with a cover of Elton John’s “Our Song.” But according to a new biography, the spectacle was much more extensive than previously reported.

In Catherine, the Princess of Wales, out this week, Robert Jobson reports that William and Kate actually lip synced to a song from the 1978 movie Grease at their Buckingham Palace reception.  “They stood holding hands in the middle of the dance floor grinning, then suddenly the opening bars of the song ‘You’re the One That I Want’ from the musical Grease came booming out,” Jobson writes, per People. “William and Catherine then began dancing around, pointing at each other, and mouthing the words with the style of the lead characters Danny and Sandy. It brought the house down.”

Though Kate hasn’t mentioned being a fan of musicals, she has shown off her love for music in piano performances and Christmas concerts. Both stars of Grease also had special ties to the royal family. In 1985, John Travolta was photographed enjoying a dance with Princess Diana at a White House reception, and he later called it “one of the highlights of my life.” In 2020, Olivia Newton-John was granted damehood, the highest honor in the British system, by decree of Queen Elizabeth for her services to charity, cancer research, and entertainment.

Despite Kate’s recent cancer diagnosis, the couple still found a way to celebrate their 13th anniversary this April, and sources told Vanity Fair, that the celebration was low-key. On their Instagram account, they shared a never-before-seen image from their wedding day, taken by photographer Millie Pilkington.