Worth noting is that the graphic novel was written at a time in which the openly fascist and borderline Neo-Nazi National Front were a highly visible, if minor, force in British politics. Then again, there's the BNP now, so it's not like that much has changed.
Artistic License: Moore has admitted he knew basically nothing about nuclear weapons when he started the comic, and so it's insanely optimistic about how many people would survive a nuclear war, which of course depends on how widespread the war is, as a limited war might lead to this situation.
Alan Moore: I came up with a character called "Vendetta", who would be set in a realistic thirties world that drew upon my own knowledge of the Gangster era, bolstered by lots of good, solid research. I sent the idea off to Dave. His response was that he was sick to the back teeth of doing good solid research and if he was to draw one more "28 model Duesenberg" he'd eat his arm. This presented a serious problem.
Anonymous has adopted the Guy Fawkes motif for its protests, which apparently tickles Moore enough that he doesn't mind that this is inspired by the movie, rather than the book.
Disowned Adaptation: Moore specifically requested that his name be removed from the film's production after Joel Silver (the producer) lied about Moore's enthusiasm for the shooting script.
Executive Meddling: It apparently spawned the title itself. While the movie was being made, someone thought it would be a good idea to outright lie and say that Alan Moore completely supported the movie. He didn't, and made that fact known by refusing any payment what-so-ever on every movie adaptation of his work afterwards. Good job!
Fake Brit: Both Portman (Israeli-American) and Weaving (Australian). However, given V's cloudy backstory and the xenophobia of the government, V may not have been a native Brit himself. Considering Weaving actually spent a good portion of his childhood and teens living in the UK, his Fake Brit status is debatable.
Meaningful Release Date: It was originally scheduled to open on November 4, 2005 (the day before Guy Fawkes Night/the 400th anniversary of the Gunpowder Plot) but was delayed four months due to Warner Bros. being unsure about its box office prospects.
The Other Marty: James Purefoy was originally cast as V before quitting due to the difficulty of acting an entire film behind a mask. Some of his six weeks worth of filming remains intact, dubbed over by Hugo Weaving.