Their names may not appear above the title, but even if they are anonymous, the most coveted among them are as vital to the success of the movies they work on than the best known A-list stars. And now the phalanx of women scriptwriters hoping to challenge the men who still dominate Hollywood have a new billion-dollar scribe leading the pack.
Melissa Rosenberg, a 49-year-old with an impressive CV of film and television work behind her, has become the world's highest-grossing female writer thanks to her success in turning the Twilight saga into a box office monster. The four films in the series, all written by Rosenberg, have contributed the lion's share of the more than $2.56 billion in worldwide revenue her movies have generated.
According to the Hollywood Reporter, the success of the latest instalment in the teen vampire franchise has now taken her past Linda Woolverton, a 20-year veteran who enjoyed her best-known success with 1994's Disney smash The Lion King. But the success of the two women is still a drop in the ocean in the vastly male-dominated film industry. A study of box office takings for 2009 by the University of Southern California found that just 13.5 per cent of the top-grossing films of that year were written by women.
Still, Rosenberg's ability to connect with the innermost desires of the Twilight series' teenage girl target audience has made her one of the hottest properties in Hollywood.
The Emmy-nominated Rosenberg began her career in television, writing episodes of teen drama The O.C. She became head writer and executive producer on Dexter, the lurid serial killer series. Rosenberg earned her big break into film by co-writing Step Up, a low budget school-set romantic drama.
The script impressed the producers of the Twilight film, who dumped an earlier screen adaptation in favour of Rosenberg's, which remained faithful to Stephenie Meyer's novel.
"One thing Harry Potter (the films) got really right was being true to the book – if not to the letter, to the spirit of the books," Rosenberg said. She retained control over the Twilight sequels following the hit first film's release in 2008.
Twilight's lucrative mix of wolves-versus-vampires CGI action and virginal romance has convinced audiences more than it has critics. The Independent's Anthony Quinn wrote of Breaking Dawn: "Melissa Rosenberg's clunking script prompted gales of derision when I saw it."
Woolverton, nine years her senior at 58, has enjoyed a range of successes besides The Lion King, which has taken $945m. She also hit paydirt with Tim Burton's 3D Alice In Wonderland, which earned $1 billion last year. In total her movies have made about $2.39bn.
In comparison with such vast riches, the money paid to scriptwriters is relatively meagre. The biggest money deal for a single script is the $5 million paid to Terry Rossio (Shrek, Pirates of the Caribbean) and Bill Marsilii for Déjà Vu, a convoluted 2006 time-travel thriller starring Denzel Washington.
It is no coincidence that the record is held by men – Steve Kloves, screen author of the Harry Potter films, is the biggest-grossing screenwriter, after his films generated $6.8bn. And the comparison for direction is even worse than it is for screenwriting. Despite Kathryn Bigelow's breakthrough, when she became the first woman to win the Best Director Oscar in 2009 with The Hurt Locker, a mere 3.6 per cent of directors on the top-grossing movies of 2009 were female.
The Centre for the Study of Women in Television and Film at San Diego State University found that women have only 16 percent of powerful behind-the-scenes jobs such as writing, directing, editing and other influential positions. The figure had fallen by a point from the peak of 1998.
Women have reached the highest echelons in Hollywood studios, however, and currently hold the chairmanship of power-houses including Disney, Fox, Sony Pictures and DreamWorks.
The most powerful women in Hollywood, according to the Hollywood Reporter, is Anne Sweeney, 54, co-chair of Disney Media Networks, who is tipped to succeed her boss, Robert Iger, and become CEO when he steps down in 2015.
Whether Rosenberg or Woolverton can make a similar leap is yet to be seen. Even Rosenberg's continued supremacy between the two of them is not yet clear. Whereas her next project is an untested young adult novel, Earthseed, Woolverton is returning to her greatest success – the Alice in Wonderland franchise.
Alice in Wonderland (2010) - $1.024 bn worldwide
Arctic Tale (2007) - $1.9m worldwide
The Lion King (1994) - $945.6m worldwide
Homeward Bound: The Incredible Journey (1993) - $41.8m worldwide
Beauty and the Beast (1991) - $377.4m worldwide
The Twilight Saga: Breaking Dawn Part 1 (2011) - $647.3m worldwide (and counting)
The Twilight Saga: Eclipse (2010) - $698.5m worldwide
The Twilight Saga: New Moon (2009) - $709.8m worldwide
Twilight (2008) - $392.6m worldwide
Step Up (2006) - $114.2m worldwide
All the best lines: Female wordsmiths
Born Marion Benson Owens in 1888, she was the first woman to win a solo Best Screenplay Oscar for The Big House in 1930. She wrote more than 130 films between 1915 and 1929 and was a close friend of the actress Mary Pickford.
Kristen Wiig and Annie Mumolo
This duo broke into the big time this year with their hit comedy Bridesmaids. They spent four years writing the movie, in which Wiig also plays the lead. Some feminists regarded the film as a triumph.
Brook Busey, who writes under the name Diablo Cody and belongs the 'Fempire' Hollywood writing group, won the Best Original Screenplay Oscar for her 2007 film Juno.
The British playwright and screenwriter penned the BBC TV series The Hour, and has already been lauded for her dialogue-craft in the forthcoming film biography of Margaret Thatcher - The Iron Lady.