To prepare for the role, Renée Zellweger gained 25 pounds, and then actually worked at a British publishing company for a month in preparation for the role. She adopted an alias as well as her posh accent and was apparently not recognized. On her desk in this office she kept a framed picture of then boyfriend Jim Carrey. Workers who did not recognize her found this to be odd, but never mentioned it to her for fear of embarrassing her.
In order to make her English accent seem more natural, Renée Zellweger retained it on set even while not shooting. Hugh Grant once noted that he did not hear her speak in an American accent until the wrap party, after the film was completed, where he heard her speak "in a very strange voice" that he soon found out was her own natural tone.
In the first scene featuring Shirley Henderson, who plays Bridget's friend, Jude, she's crying in the bathroom (which the narrator says she does often). Shirley Henderson also played "Moaning Myrtle" in the Harry Potter films, where she spends her time - crying in the bathroom.
When Helen Fielding wrote the novel "Bridget Jones's Diary", she based the character of Mark Darcy on Colin Firth's depiction of Mr. Darcy in Pride and Prejudice (1995). In addition to the inside-joke casting of Colin Firth as Mark Darcy, there are several other allusions to Jane Austen's story: Mark disparages Bridget to his mother within earshot of Bridget. In "Pride and Prejudice", Mr. Darcy disparages Elizabeth to his friend Mr. Bingley within earshot of Elizabeth. Daniel Cleaver lies to Bridget about a dispute between him and Mark, claiming Mark stole his fiancée; in fact, it was the other way around. In "Pride and Prejudice", it's a dispute between Mr. Wickham and Mr. Darcy, and Wickham lies about who's at fault. The Darcy in both stories fails to disabuse the heroine's misinformed notion until it's almost too late. Bridget works at Pemberley Press; Mr. Darcy lives at Pemberley estate. Crispin Bonham-Carter was in both productions (his scenes were cut out of the film, although he can still be seen in the job-quitting scene and can also be seen at the Kafka book launch where Bridget asks Salman Rushdie where the toilets are - he is seen as the man on the left in the conversation). When Bridget stops at a mall to see her mother, she begins the scene by saying (in a voice over) that, "It is a truth universally acknowledged that as soon as one part of your life starts looking up, another part falls to pieces." This is an update of the famous opening lines of "Pride and Prejudice": "It is a truth universally acknowledged, that a single man in possession of a good fortune, must be in want of a wife."
The film has different end-credits in different countries. In Europe, Australia and Latin America the credits show a montage of stills plus "interviews" about Bridget and Darcy with Daniel Cleaver, Mark Darcy's parents and Bridget's boss. In America, they show a young Bridget and Mark running around the backyard and paddling pool in a home video. The "interviews" can be found as the final deleted scene on the North American DVD, while the North American credits are found in the 'Deleted Scenes' material on the European DVD.
Both leading actors' names, Colin Firth and Hugh Grant, are mentioned in the book. The first on "Tuesday 24 October" and the second on "Wednesday 16 August". Colin Firth is himself a featured character in the book's sequel, Bridget Jones: The Edge of Reason (2004). While audiences were eager to see Hugh Grant play a character opposite to his usual type-cast, it is ironic that original author Helen Fielding describes him, in real life, as being more like Daniel Cleaver than any of his "normal" roles.
All of the characters who appeared in this movie and who reappeared in the sequel were played by the same actor or actress with the exception of Mrs. Darcy who was played by Shirley Dixon in the sequel replacing the late Charmian May who sadly passed away after the release of the first movie and before the making of the second movie commenced.
When Bridget is having dinner with Shazza, Jude and Tom and asks what they would do if their employee made a "harmless little mistake like that" we are led to believe that she's referring to the F.R. Leavis incident. But in one of the scenes that were cut it shows Bridget (on the same day) pitching a marketing idea to one of their writers, the only problem is that she mistakes Michael Naughton, the author of "Teddy Knows Best", for Michael Harper, the author of "The Red Door". This is what she was referring to in the original scripted version of the film.