An imperial visit at Versailles
In the 18th century international travel was far more expensive, dangerous and difficult than we can imagine today, and of course much slower. A princess who married into a foreign court might never see her family again. State visits by foreign monarchs were exceptional affairs.
The etiquette of Versailles, while specific on the reception of foreign ambassadors, was not adapted to visiting royalty. As a practical matter any such guests, whenever they did come to Versailles, elected to travel under transparent pseudonyms to avoid any awkwardness.
Thus Grand Duke Paul of Russia, future Tsar Paul i, and his wife Grand Duchess Maria Feodorovna, née Sophia Dorothea of Wurtemberg, visited Versailles in 1782 under the assumed names of Comte et Comtesse du Nord. The Grand Duchess, later Empress Maria Feodorovna, had grown up in Montbéliard, an independent principality within French territory.
Elena Maria at Tea at Trianon has an excellent post on this visit.