The scene where Mia slips and falls in the bleachers was real. Anne Hathaway had slipped on a puddle while doing the scene, and director Garry Marshall thought it was so funny, he inserted it in the final cut.
The picture of Mia's deceased father next to her music box is Anne Hathaway's real-life father (Gerald T. Hathaway). He also appears to be writing the letter to her while fishing.
Mia's cat, Fat Louie, was Anne Hathaway's pet in real life. Four different cats played the role. One who allowed people to carry it, one who could sit still, another who would jump, and the last one, who sits on the envelope at the end of the movie.
During auditions, Anne Hathaway fell out of her chair, and was immediately given the part as clumsy Mia Thermopolis.
When Mia accidentally sets the man's arm on fire, the flames were supposed to go out when he puts his arm in the ice bucket, but they didn't. Anne Hathaway panicked and threw the glass of water on it, which was not scripted.
Lauren Maltby: Then-Disney Channel Movie Surfer Lauren Maltby helped edit one of the trailers of this movie. She even had a cameo in the beach party scene as well.
Garry Marshall: Guest at Genovia's annual independence ball. His sister Penny Marshall is another guest.