Mia Thermopolis, the fictional star of the book series and film franchise, The Princess Diaries where Anne Hathaway stars as the royal princess, has sent her well wishes to the couple on their new addition.
The Princess of Genovia’s congratulatory message was shared by the author of the book series, Meg Cabot on her Twitter account.
She tweeted: “HRH Princess Mia Thermopolis of Genovia wishes to extend her warmest congratulations to the Duke and Duchess of Sussex on the birth of their daughter Lilibet “Lili” Diana Mountbatten-Windsor.”
Despite, Mia Thermopolis being a work of fiction - fans of the franchise were royally entertained by the tribute.
Many made comparisons between Mia and Lilibet as both being American princesses. Lili was born in Santa Barbara Cottage Hospital, in the US and will have American citizenship.
While others shared their nostalgia for reading the books and watching the 2001 and 2004 films growing up.
But Princess Thermopolis wasn’t the only royal congratulating the Duke and Duchess of Sussex on Friday.
Queen Elizabeth; Prince Charles and Camilla, Duchess of Cornwall; Prince William; Kate Middleton, and Prince Eugenie congratulated the couple on their royal arrival.
Lilibet, who is named after the Queen’s family nickname, is now eighth in line to the throne - behind her brother Archie.
She is the Queen’s 11th great-grandchild, and the second British royal to be born in the US.
The first being Maud Windsor - the eldest grandchild of the Queen’s cousin, Prince Michael of Kent who was born in LA in 2013.