Trivia: In the opening scene where Mia is introduced and waves to the crowd from atop a staircase, (wearing a big red dress) she accidentally flings a bracelet off her wrist, where a footman catches it. That is the same footman who catches the snail Julia Roberts flings in Pretty Woman, and he uses the same line "It happens all the time".
Trivia: In the scene where Mia sees all of the past royals in her family the paintings on the walls, they are of writers and producers.
Trivia: When Julie Andrews says that she never slides, she adds that she "has done a lot of flying". That is referring to Mary Poppins, which she starred in as Mary Poppins.
Trivia: The girl dancing on the stage with the Queen and Raven is Julie Andrew's granddaughter.
Trivia: The song, "Your Crowning Glory", was the first time Julie Andrews sang in public or on screen since she had throat surgery in 1991. She reportedly nailed the song on the first take, and brought tears to the eyes of the crew present.
Trivia: Most of the flowers used throughout the movie are mostly fresh flowers personally placed and arranged by Julie Andrews.
Trivia: During Mia's coronation there is a marching band, and two men are beating drums on stands. The man on the left is director Garry Marshall and the man on the right is the director of photography.
Trivia: There is a deleted scene which explains how the ramp came to be. Apparently, all of the royals had their birthdays during the rainy season, so King Rupert had this ramp made so birthday parties could be celebrated inside, out of the rain.
Trivia: Lord Crawley and his identical twin brother acknowledge each other by their first names, Jerry and Dean. This is a reference to Dean Martin and Jerry Lewis, one of the most successful comedy teams of the 1950s.
Trivia: Stan Lee makes a cameo as an attendee at Anne Hathaway's wedding.
Trivia: The choir director is Anne Hathaway's real-life mother, Kate McCauley Hathaway.
Trivia: At the Royal Garden Party, Princess Mia asks a guest how her three grandchildren, Lily, Sam & Charlotte are doing. These are the names of director Garry Marshall's three grandchildren. The guest Princess Mia is speaking to is Barbara Marshall, Garry Marshall's wife.
Answer: My guess is because Mia and Michael didn't actually start dating until the third Princess Diaries book. The second and third books were all about Mia trying to get Michael to go out with her, and since they went out at the end of the first movie, they couldn't base the second movie on the second book.