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, and getting his name removed from them. Good job, Joel!
Fake Brit: Both Natalie Portman (Israeli-American) and Hugo 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.
Hey, It's That Place!: The disused Aldwych London Underground station features extensively, both as the location for one of the biological attacks with the name "Strand" (a previous RL name for the station) and in the climax as Victoria.
Looping Lines: Hugo Weaving as V had to dub all of his lines, both because of the mask and because the character was originally played by James Purefoy, who left a few weeks into filming. Due to the mask, they only had to redub rather than reshoot Purefoy's scenes.
The Other Marty: James Purefoy was originally cast as V, but reportedly he wasn't coming across with the right performance and wasn't acting effectively through the mask, so Hugo Weaving replaced him. Some scenes of V in the film are actually Purefoy in the suit and not Weaving, but with Weaving's voice dubbed over Purefoy's.
The Red Stapler: Demands for Guy Fawkes masks for Halloween skyrocketed after the film came out. The movie was also what standardized the Guy Fawkes mask, which were typically home made before its release.
Release Date Change: 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.
Hilary Henkin wrote an early adaptation of the graphic novel, which was singled out as one of Hollywood's best unproduced scripts in a 1993 Los Angeles Times article. Her script was described as a "wild, over-the-top saga", and a cross between Les Misérables and A Clockwork Orange. It bears little, if any, relation to the finished product, with the inclusion of overtly satirical and surrealistic elements not present in the graphic novel, as well as the removal of much of the novel's ambiguity, especially in regard to V's identity.