Behind the tiaras and trumpets of a royal state visit, there are sometimes eyebrow-raising moments being served.In July, Buckingham Palace announced that President Trump and his wife, First Lady Melania Trump, would pay a state visit to the U.K. from Sept. 1719. King Charles III hosted the couple at Windsor Castle.Trump is the first U.S. president to be invited for two state visits by a British monarch. The late Queen Elizabeth II hosted the U.S. president in 2019 during his first administration.KATE MIDDLETON AND MELANIA TRUMP TEAM UP FOR FIRST-EVER JOINT OUTING DURING HISTORIC STATE VISITWhile the festivities provided plenty of pomp and pageantry, royal experts told Fox News Digital that no gathering could ever rival the late monarchs unforgettable encounter with a controversial guest.According to the royal familys website, foreign monarchs, presidents or prime ministers are invited to visit the monarch on the advice of the Foreign and Commonwealth Office. Usually, on the evening of the first day, visitors are hosted at a state banquet. Around 150 guests are typically invited based on cultural, diplomatic or economic ties to the visiting country.While unexpected gaffes are rare during such highly formal events, they do happen."One of the most calamitous state visits involved Romanian dictator Nicolae Ceauescu and his wife, Elena, in 1978," royal expert Richard Fitzwilliams told Fox News Digital. "They were obsessed with being bugged inside Buckingham Palace and only felt safe in the gardens. When Queen Elizabeth II saw them, she reportedly hid behind a bush to avoid speaking with them.""She thought they were ghastly," he added.Royal author Robert Hardman previously described the visit in the ITV documentary "Queen: Inside the Crown.""On the occasion when they were staying, she took the corgis out for a walk in the palace gardens, and she could see [them] coming the other way," said Hardman, as quoted by People magazine.CLICK HERE TO SIGN UP FOR THE ENTERTAINMENT NEWSLETTER"She thought, 'I really can't face talking to them,' so for the first and only time in her life, she actually hid in a bush in the palace gardens to avoid her guests."The outlet noted that, as with all state visits to the U.K., the decision to invite the communist dictator to Buckingham Palace was made by the British government."The press started to question the foreign secretary," said Hardman in the special, adding that the media asked, "Why are we inviting this monster to come to Britain?"WATCH: QUEEN ELIZABETH'S UNEXPECTED BOND WITH AN AMERICAN COWBOY REVEALEDIts unknown if Ceauescu spotted the queen hiding in the foliage. However, it was made crystal clear to the British government that the queen disapproved of the state event, the outlet reported."The queen puts up with many different people, but Ceauescu was too much for her," former British Foreign Secretary Lord David Owen said in the special. "She made it quite plain she didn't like that visit!"It wouldnt be the only time the late monarch was "extremely displeased" during a state visit, said Fitzwilliams."Zaire's President Mobutu Sese Sekos wife, Marie-Antoinette, smuggled her dog in her luggage during their state visit in 1973," Fitzwilliams said. "An angry queen ordered it removed, and her corgis quarantined."The president attempted to explain the mishap during a speech, arguing that the dog was of British heritage, the U.K.s Express reported."President Mobutu of Zaire was definitely a low point," said Hardman in the ITV documentary. "The queen was very unhappy about that."LIKE WHAT YOURE READING? CLICK HERE FOR MORE ENTERTAINMENT NEWSAccording to British royals expert Hilary Fordwich, one major faux pas reportedly occurred when an American president came to town."One of the worst gaffes was President Jimmy Carter kissing the Queen Mother right on her lips during the state dinner at Buckingham Palace," she claimed. "The Queen Mother later told her biographer, He is the only man, since my dear husband (King George VI, Queen Elizabeth IIs father) died, to have had the effrontery to kiss me on the lips."Despite the Queen Mothers recollection, the former president denied the claim."More than two years later, there were reports in the British papers that grossly distorted this event, stating that I had deeply embarrassed her with excessive familiarity," Carter wrote in his 2016 autobiography, as quoted by People magazine. "I was distressed by these reports but couldnt change what had happened nor did I regret it."For British broadcaster and photographer Helena Chard, its the Obamas who stood out to her."When they were there in 2009, former first lady Michelle Obama put her arm around the late queen," she recalled. "Everyone always says you cant touch the queen or king. But actually, theyre not so starchy."In 2018, Obama described the candid moment in her memoir "Becoming," noting she and the queen were bonding over the painful shoes they were wearing that day."I then did whats instinctive to me any time I feel connected to a new person, which is to express my feelings outwardly," she wrote, as quoted by Harpers Bazaar. "I laid a hand affectionately across her shoulder."The queen, England's longest-reigning monarch, died in 2022 at age 96. But surprising moments have already made an appearance at state visits during King Charles's reign.French President Emmanuel Macron recently showed off his charming side during the state banquet at Windsor Castle in July of this year.The 47-year-old was spotted politely helping to pull out Kate Middletons chair and waited for her to sit before he took his own seat beside her. During a toast, cameras captured him winking at the Princess of Wales, which went viral on social media.For anyone lucky enough to receive an invitation, Chard has a key piece of advice to avoid a mishap."Queen Elizabeth traveled to so many countries on the royal yacht Britannia," she said. "And she would always receive strange gifts, like roasted pigs. Various animals were given. I think even a big crocodile. What do you do with things like that? I think sometimes they were thrown overboard, and the sharks used to eat them."