It has long been known that the Duke and Duchess of Cambridge would be visiting Wales today as part of the Platinum Jubilee celebrations, but they brought two surprise guests with them!

Prince George and Princess Charlotte appeared at Cardiff Castle today with their parents to the delight of the crowd. (The foursome wore a patriotic red, white, and blue color palette, with Kate wearing a custom Eponine London red coat, Charlotte a double-breasted amaia blue coat, and William and George in navy pants and jackets.

PEOPLE magazine noted, "The day was especially poignant for 8-year-old George, who visited Cardiff in March 1991 with his mother, Princess Diana, and father, Prince Charles. (Both William and later George would one day become Prince of Wales before becoming King.)

While in Wales, the Cambridges met musicians, including joining an orchestra on stage. The live entertainment will be especially enjoyable for George," wrote PEOPLE.

"Kate had previously revealed that the young prince is learning to play the guitar.

The family met with close friends gathered before returning to London, where both William and Charles will pay their respects to Her Majesty the Queen at a platinum party at the palace tonight. The Queen will see a concert at her home at Windsor Castle, having missed the Derby at Epsom Downs today. (Princess Anne attended in her place.)

The Cambridges' visit to Wales is one of many events that members of the royal family will be making across the UK this weekend for the Queen's Platinum Jubilee. Yesterday, Anne and her husband, Vice Admiral Tim Lawrence, visited Scotland, while Prince Edward and Sophie, Countess of Wessex, are visiting Northern Ireland.

And while the Cambridges were in Wales, they were not too busy celebrating Lili's first birthday on social media, as Prince Charles and Camilla were.