Typically, a screenplay is the backbone or blueprint for a movie—but occasionally, a film will go into principal photography without a finished script, with writers frantically trying to complete scenes for a quick and dirty production. Sometimes, it works, and sometimes ... it doesn't.

1. Sunset Boulevard

Billy Wilder's Academy Award-winning film noir Sunset Boulevard went into production with the script unfinished. This was partly due to poor production planning, but also Wilder and his co-producer/co-screenwriter Charles Brackett's plan to get the film made without getting objections from censors and studio executives. Wilder and Brackett used the working title A Can of Beans and submitted pages to censors and executives piecemeal during production to disguise its cynical and scathing look at the studio system.

After a preview screening of Sunset Boulevard, MGM executive Louis B. Mayer told Wilder, "You have disgraced the industry that made and fed you! You should be tarred and feathered and run out of Hollywood!"

2. Lawrence of Arabia

David Lean's masterpiece Lawrence of Arabia bore little resemblance to its original script, penned by screenwriter Michael Wilson. Lean brought on British playwright Robert Bolt to re-focus the film on T.E. Lawrence, played by Peter O'Toole, instead of its overly political point-of-view with the Arab Revolt. The late re-write didn't stop the production; Lean started shooting without a finished script. To further complicate the production, Bolt was arrested due to his involvement in an anti-nuclear weapons demonstration, which hampered the screenplay's completion.  

3. Iron Man

According to star Jeff Bridges, Iron Man—the first movie in the Marvel Cinematic Universe—went into production with just an outline when the studio rushed production in March 2007 to make the movie's May 2008 release date. "They had no script, man. They had an outline," the actor, who played Obadiah Stane (a.k.a. Iron Monger) told io9. "We would show up for big scenes every day and we wouldn't know what we were going to say. We would have to go into our trailer and work on this scene and call up writers on the phone, 'You got any ideas?' Meanwhile the crew is tapping their foot on the stage waiting for us to come on. You would think with a $200 million movie you'd have the sh*t together, but it was just the opposite. And the reason for that is because they get ahead of themselves. They have a release date before the script."

4. Edge of Tomorrow

The science fiction film Edge of Tomorrow began production in 2012 with just a rough outline of its action and story, which was based on a Japanese best-selling novel entitled All You Need Is Kill. However, according to producer Erwin Stoff, Doug Liman's direction made it possible to press forward without a screenplay.

"It definitely is not the most calm-inducing experience to be facing the start date without a script. You have to have a cast-iron stomach," Stoff told the Los Angeles Times. "What made me hire Doug is, he has an ability to take a tried and true genre and find something completely new in it, push the familiar genre elements to the back and use the genre to explore something brand new and completely original."

5. Casablanca

Most movies shoot out of order for budgeting and logistic reasons. However, when Casablanca started shooting on May 25, 1942, its scenes were shot in sequential order because only the first half of the script was ready for production. Instead, its writers completed the screenplay during production, while they had Casablanca's source material—a stage play titled "Everybody Comes to Rick's"—as an outline and guide. Throughout its entire shooting schedule, Casablanca went through four different screenwriters to re-write and finish its screenplay.

6. Topaz

Topaz, one of Alfred Hitchcock's last films, is based on the novel of the same name. Author Leon Uris initially started adapting his own book for the big screen, but Uris and Hitchcock didn't see eye-to-eye on the direction of the movie (Hitchcock wanted more black humor and a humanized villain), so the author left the project just a few days before shooting was scheduled to begin. Hitchcock hired screenwriter Samuel Taylor to complete the screenplay, while Topaz went into production without a finished script. It was reported that scenes were shot only hours after they were written.

7. Alien 3

Due to the Writers Guild of America strike in 1987, development on Alien 3 was put on hold until the strike was resolved. Once Hollywood writers were able to go back to work, a two-film treatment for Alien 3 and Alien 4 was scrapped—but not before set designers started building expensive sets and models based on concept art for the two films. A story had to fit around what was built and waiting at Pinewood Studios in England, and Twentieth Century Fox had already announced a release date of 1992, before a director or script were finalized. The production went through two directors—Renny Harlin and Vincent Ward—before landing on David Fincher for his directorial debut.

With $7 million sunk into developing the story and pre-production, Alien 3 started shooting without a finished screenplay in 1991. Fincher didn't have enough time to prepare the film for a proper production and was struggling with re-writing the script and re-shooting scenes, studio interference, and a looming release date. After production was complete, Fincher left the project before the movie was assembled in editing.

“We have had to make a lot of changes in the script as we’ve gone along,” star Sigourney Weaver told Empire Magazine. “We were building the sets before we had a script and having to cast it quickly, because of time concerns. That was not the way that Fincher wanted to do his first film."

8. Jaws

While the blockbuster Jaws is now seen as a milestone in cinematic history and Steven Spielberg's career, its production was plagued by numerous difficulties—filming in the open water instead of a tank on a studio stage at Spielberg's insistence, mechanical problems with the shark, and the lack of a completed script while shooting. As a result, the production took more than 100 days to complete with a budget that ballooned to three times its initial cost. "We started the film without a script, without a cast and without a shark," said Richard Dreyfuss of his experience making Jaws. Screenwriter Carl Gottlieb was brought on to finish and re-write the script during principal photography in 1974.