Alan Moore drew upon a comic strip idea submission that the DC Thomson scriptwriting competition rejected in 1975. "The Doll" involved a transsexual terrorist in white face makeup who fought a totalitarian state during the 1980s.
Moore's original idea was to set the book in the 1930s, because Dave Lloyd at the time was known for his skill in drawing automobiles from that era and for his level of "good solid research". A single letter from Lloyd upended this plan.
"Dave then let me know that he was sick to the back teeth of good solid research, and if he had to draw one more '29 De Soto, he'd gnaw off his drawing arm."
Disowned Adaptation: Alan 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 whatsoever 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 - his accent is certainly authentic.
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.
Irony as She Is Cast: John Hurt, who famously played an oppressed victim of a dystopian Britain in the movie adaptation of Nineteen Eighty-Four, plays Sutler, the ruler of a dystopian Britain, here.
One-Take Wonder: Evey's head buzzing scene was done in one take. James McTeigue utilized three cameras for the scene.
Orphaned Reference: After V blows up the Old Bailey, Finch reports that they found traces of the explosives used at both sites. In an earlier draft, V blew up both Parliament and the Old Bailey in the opening.
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.
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.
"Eggy in a basket" became a pretty popular homemade breakfast after the film's release.
Before hitting it big with The Matrix, The Wachowskis, avid fans of the graphic novel, wrote a draft screenplay in the mid-nineties that closely followed the original. They revised the screenplay during post-production of The Matrix Reloaded and The Matrix Revolutions and offered the director's chair to James McTeigue.