The Search for a Real-Life Cinderella! Someone Left Their Shoe at the Castle After Prince Christian's Birthday

Prince Christian of Denmark's 18th birthday gala ended with a mystery after a single heel was found following the celebrations at Christiansborg Palace

Prince Christian of Denmark's 18th birthday gala was straight out of a fairy tale — and there's even a real-life Cinderella missing a shoe!

Royals from around Europe (including a number of fellow future monarchs!) gathered on Sunday for the celebration at Christiansborg Palace in Copenhagen. The guests sported tiaras, ballgowns, military uniforms and sashes showing their honors — but one attendee left the dinner minus an important accessory.

On Monday, the Danish royal palace had some fun on Instagram by posting a photo of a single sparkling shoe that was found after the festivities wrapped.

"Is it Cinderella who forgot her shoe last night?" courtiers captioned the snap.

"When the guests at Her Majesty the Queen's gala dinner yesterday had gone home, this lonely stiletto shoe was left at Christiansborg Castle," they continued. "The owner is welcome to contact us to get it back."

Related: 5 Future European Monarchs Pose for Epic Photo at Prince Christian of Denmark's 18th Birthday Gala

Although it was a formal gala, there was still plenty of fun, which may have prompted some guests to take off their shoes for some better comfort. The night included a special performance that Queen Margrethe set up behind the scenes to surprise her grandson, who is currently second in the line of succession to the Danish throne.

"The dancefloor was lit when Benjamin Hav & the Family gave a concert after the gala table," the palace shared with a video on Instagram. "The concert was Her Majesty the Queen's surprise to all the guests."

The clip showed Prince Christian clapping along to the music — and his little brother, Prince Vincent excitedly jumping up and down!

One person who certainly didn't leave her heel behind was Princess Catharina-Amalia of the Netherlands. The 19-year-old heir to the Dutch throne paired her royal blue caped gown with Queen Emma of the Netherlands' sapphire tiara and a recognizable pair of shoes: Manolo Blahnik's satin pumps featuring a silver buckle adorning the pointy toe. It's the same style that Sarah Jessica Parker's character, Carrie Bradshaw, wore in Sex and the City for her wedding to Mr. Big as her "something blue" for the walk down the aisle.

Princess Amalia isn't the only royal who has the shoes in her closet. Kate Middleton sported the same pair in green for her first official joint portrait with Prince William.

Prince Christian's birthday gala doubled as a royal reunion, and five future European monarchs posed together for a group picture.

Prince Christian was all smiles beside Princess Estelle of Sweden, 11, Princess Ingrid Alexandra of Norway, 19, Princess Catharina-Amalia and Princess Elisabeth of Belgium, 21, in the snap that the Danish Royal House shared on Instagram.

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The guest list also included Crown Prince Haakon and Crown Princess Mette-Marit of Norway, Princess Ingrid Alexandra's parents. Princess Estelle of Sweden similarly attended alongside her parents, Crown Princess Victoria and Prince Daniel.

The Scandinavian royal families are extremely close in both their royal duties and their personal connections. It's not rare to see the Swedish, Norwegian and Danish royal families vacationing together or attending significant events like weddings, funerals and christenings. They also often act as godparents to each other's children — in fact, Princess Victoria, Prince Haakon and Princess Mette-Marit are all godparents to Prince Christian!

Related: Future Queens of Europe! Meet All the Female Heirs Set to Take the Throne

Prince Christian's birthday gala also welcomed representatives from some of Denmark’s youth organizations plus young people “who have distinguished themselves in the world of sport, art and culture.” Extending the guest list, the palace invited around 200 young people from the Danish Commonwealth, allowing each of Denmark’s municipalities, Greenland and the Faroe Islands to invite two 18-year-old guests to the party.

In addition to the gala dinner, Prince Christian's milestone birthday will again be marked on Nov. 14, when he attends a meeting of the Council of State (which is comprised of government ministers) and declares that he wishes to comply with the Danish constitution.

“Prince Christian will then be able to be appointed as head of state. Prince Christian will not get a seat in the Council of State until a change of throne has taken place,” the Danish Royal House said.

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