The Prince of Wales became the Prince of Denmark as he joined acting royalty on stage to mark the 400th anniversary of Shakespeare's death.
Charles made a surprise appearance as Hamlet in a star-studded televised gala performance in the Bard's birthplace in Stratford-upon-Avon.
The town's riverside Royal Shakespeare Theatre hosted performances from famous names including Dame Judi Dench, Sir Ian McKellen, Benedict Cumberbatch and David Tennant as acting greats paid tribute to the playwright's continuing legacy.
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UK marks 400 years since Shakespeare died
Charles, who had been watching the Shakespeare Live! From The Royal Shakespeare Company show with the Duchess of Cornwall, was heard to speak from the wings, asking: "Might I have a word ... "
Then followed the opening lines to what is one of Shakespeare's best-known soliloquys: "To be or not to be, that is the question."
The show, which featured Shakespeare-inspired work spanning a range of musical genres, was screened live to 368 cinemas in the UK and Europe.
The surprise royal appearance marked the end of a day celebrating the town's most famous son.
Earlier Charles visited the last resting place of the Bard at Holy Trinity Church, laying a wreath at his grave, after touring the site of a new garden located on what was the location of the world-renowned playwright's former home.
The Prince was shown an inscription of Shakespeare's grave stone which reads "cursed be he who moves my bones".
The Rev Patrick Taylor explained how it was believed the writer had his grave inscribed with the curse because he was "petrified" his remains might be moved to a nearby charnel house, which lies behind a church door just a yard or two from the grave.
Charles replied: "It certainly reminds you of your mortality".
Charles had a little earlier toured the New Place on the former site of Shakespeare's town house, now long since demolished, where a garden is being established to remember the poet's legacy and works.
Earlier, US president Barack Obama was treated to a special performance of scenes from Hamlet at Shakespeare's Globe Theatre in London.
Shakespeare, who penned almost 40 plays, over 150 sonnets, and coined well-known phrases still widely used to this day, died in 1616.
