(at around 38 mins) During the birthday dinner scene, Anna Scott is asked how much she made on her last film, and her reply is $15 million. This is the amount Julia Roberts was paid for her role in this movie.
The house with the blue door where William lives is a real residence; it once belonged to this movie's screenwriter, Richard Curtis.
(at around 53 mins) The bit where Anna Scott tells off the diners in the restaurant was not in the script.
(at around 1h 28 mins) The long shot where William Thacker walks through Notting Hill during summer, fall, winter, and spring was actually four different shots, all filmed the same day. Computer technology morphed Hugh Grant seamlessly from one shot to the next.
(at around 38 mins) When Bernie, unaware of Anna's level of fame, asks her how much she made in her last movie, Julia Roberts ad libbed the number. Initially in the script and during rehearsals, she said $10 million. In future takes, she changed it to $12 million. In the third take of her close-up, she said $15 million. Hugh Bonneville later asked Roberts why she kept changing the figure. She replied, "I'm kind of tired of low-balling!'
Matthew Modine: (at around 17 mins) as Anna's costar in the black-and-white movie that William and Spike watch on television.