Revealing mistake: In the first scene when Bridget makes her way up her parent's driveway, you can see her shadow against the cobbled post. However, the sun isn't out and it's cloudy, cold weather overhead. (00:01:15)
Continuity mistake: When Bridget writes her diary on 1st January, we see the fridge in the background at floor level, alongside other kitchen units. But later, just after Daniel has announced his engagement to Lara, Bridget opens the fridge to "eat the entire contents" - the fridge is now on the sideboard, with no units beside it, also its decorations are different. Later when Bridget is cooking, she opens the fridge and looks in - she is crouching in front of it, as if it is at floor level again. (00:07:36)
Continuity mistake: When Bridget is making her resolutions, she says, 'Put last night's knickers in the laundry basket.' But if you read her diary as she's writing in it, she doesn't mention this resolution, it says 'Lose 30 pounds,' then goes on to the third resolution. (00:08:00)
Continuity mistake: Tom is changing the fascia of his mobile phone. When we first see him, he is holding the phone up to his shirt and the fascia is blue, he then puts the phone down near to Bridget. It then cuts back to Tom and the phone has moved nearer to Jude and the fascia is green. Tom then opens the box in front of him and hold the blue fascia up so it falls out of the plastic wrapping completely, just before a man comes up to ask him if 'he's the bloke who sang that song' he is getting the blue fascia out of the plastic wrapping again. (00:10:50)
Continuity mistake: When Bridget, Daniel and the other guy are in the lift at the start, Bridget is in the centre of the lift. The other guy gets out and Mr. Fitzherbert replaces him. Then Daniel gropes Bridgets bum and we see them all get out - Bridget is suddenly in the corner, but the whole time she never moved. (00:15:00)
Continuity mistake: When Shazzer talks about introducing people with thoughtful details, Jude taps off her cigarette ash. Seconds later, she's seen with at least half an inch of ash on her cigarette. (00:16:55)
Continuity mistake: When Bridget is getting dressed for her big date with Daniel, her tights are over her undies; later, when he's going up her skirt, the tights are clearly under her big ugly undies. (00:17:50 - 00:26:00)
Continuity mistake: When Bridget and Daniel have gone back to his apartment and they are kissing on the floor and he discovers her enormous panties, she is trying to keep him from checking them out again. In one shot the strap of her dress is up over her shoulder, then it's down off her shoulder, then back up again. (00:26:15)
Continuity mistake: While Bridget and Daniel are driving to their "full-blown mini-break holiday weekend", Bridget lifts the sunglasses over her forehead with her left hand and holds the scarf at her neck with her right hand, but in the next shot before her scarf blows off her hands are in the opposite positions. (00:31:10)
Continuity mistake: At the tarts and vicars party, Bridget and Mark almost start arguing about Daniel and 'Mark's past behaviour'. Look at Bridget's hair between when she says 'I think he would say the same about you given your past behaviour' and when Natasha calls Mark over - Bridget's fringe changes shape in the three different shots. (00:39:30)
Visible crew/equipment: During the scene when Bridget and Cleaver are talking about Lara in his office you can see the film crew moving about in the reflection of the glass walls (and presumably the director sitting in a chair). This cannot be office workers as his office is raised from ground level. (00:45:05)
Continuity mistake: When Bridget is quitting her job and Daniel is trying to convince her to stay, you can see a woman behind him, hanging at the door of his office. She's already half inside, but there was no other person in Daniel's office apart from him and Bridget, and she wasn't seen coming into the office. (00:49:50)
Continuity mistake: After Bridget sprays the contents of the blender all over herself, there's a splodge on her right cheek - it changes shape when she answers the door. (01:01:10 - 01:02:00)
Continuity mistake: When Bridget and Mark prepare the blue soup, Mark stirs the soup with his right hand. In the close-up you can see a left thumb holding the spoon. (01:02:25)
Continuity mistake: After Mark Darcy and Daniel Cleaver fight in the street and Bridget goes to comfort Cleaver, Mark Darcy flings his jacket over his shoulder as he walks off. You can see very clearly that the white lining of the sleeve, flapping around as he walks. When the camera cuts to his receding back, the jacket is perfectly flat and smooth down his back, and the lining is no where to be seen. (01:12:20)
Revealing mistake: When they're driving back to the Darcys' in the snow, you can see that as they pass through the village near the house, the snow on the ground is in fact a white ground sheet and has not been pulled up to the edges of the wall surrounding the green. (01:17:25)
Continuity mistake: While her friends are waiting in the car for Bridget, wanting to take her to Paris, she is standing in front of her flat as Mark walks over. When they talk, the folds in the scarf around her neck very noticeably change in some of the close-up shots of her. (01:25:40)
Continuity mistake: Mark Darcy is in Bridget's flat and he notices the diary under a folded newspaper and some magazines. In this front shot, he puts the magazines down next to the newspaper and pulls the diary out from under the newspaper. In the next close-up looking down at the table when he holds the diary, the folded newspaper is no longer there. When Bridget walks into the room after Mark leaves, in this front shot of the table, the newspaper is under the diary that Mark had put down. When Bridget comes back from the window, in the close-up looking down at the table, once again the newspaper is not under the diary. (01:27:30)
Factual error: No British woman measures her weight in pounds only - always stones and pounds, or kilograms (a concession to the Americans but it sounds really odd to us Brits). Yes, in the American printing of the book it's always only pounds as well, but that's for the same reason, and still wrong.
Factual error: After all the running about at the end in the snow, no one's breath seems to be condensing.
Answer: Lots of times in book-to-movie situations and even in some remakes, the producers/writers/directors change names or events. It can be because of personal issues, legal ones or it can even be spur of the moment. it can also be unintentional,when they change it without the specific INTENTION to change it. I think in this case it was more likely that the character/or their name didn't have too much of an impact on the story line, so they didn't feel a pressing need to keep it the same.