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 she (Julia Roberts) was paid for her role in Notting Hill (1999).
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.
As he explains in the published screenplay, in Richard Curtis's original conception of the story, Honey (Emma Chambers) was a worker in the record store across from his bookshop and Anna's romantic rival for his affections. The film would have ended with William choosing her over the fantasy that Anna represented. Curtis decided that he could not just dismiss Anna, however, and so he made Honey into William's sister instead.
The park bench used in this film now 'lives' in Queens Gardens in East Perth, Western Australia. A local Perth resident anonymously donated the bench to the City of Perth and it now *really does* live in a beautiful garden that is locked at night.
The rooftop scene in which William and Anna practice her lines for the submarine movie was shortened and edited to remove some swearing from Anna that would have precluded a PG 13 rating. The extended scene is on the DVD.
The house with the blue door used in the movie was sold the year following the release of the movie. The original blue door was removed and auctioned. The replacement door was painted black so that no one would recognize it. Soon however, someone later spray painted on the wall next to the door, "This is the Hollywood door." A different house was used when Thacker and Anna are practicing her lines on the roof.
The real Travel Bookshop had a sign in its window saying "We're almost famous." It would sell non-travel books when it fitted in with a theme. For example, selling Martin Amis's "London Fields" when doing a Notting Hill theme.
Despite Thacker's protestations, it seems that his store does *not* just sell travel books. On the shelf in the background (visible clearly in a later scene where he is receiving the gift from Anna), there is a copy of Comics, Comix & Graphic Novels by Roger Sabin. (It's a big orange hardcover.)
The blue door was auctioned at Christie's Film and Entertainment sale in London. Soon after, graffiti appeared on a wall close by saying something along the lines of "R.I.P. blue door" next to the new door. The original blue door is now on a property in Hope Cove, Devon.
Omid Djalili plays the Cashier at the Coffee Shop (uncredited) - he was filming The Mummy (1999) at the same time at the same studios so was conscripted to fill in the part, very conveniently. (Blink and you could miss him serving Hugh Grant the orange juice that he soon spills on Julia Roberts.)
All the lead characters except Anna and William are not quite 'normal' and all of them are under-achiever in any specific way, even the girls who were being met by William for arrange marriage were not quite so normal.
The trivia item below may give away important plot points.
The Henry James movie in which Anna stars is based on James' novella "The Siege of London", as indicated in the paper Max tosses to William in Tony's now defunct restaurant. Anna plays Mrs. Headway, much married and divorced, bold and outspoken, from the "Wild West" in America.