In 2005, while on the London set of V for Vendetta (2005), Natalie Portman gave a copy of the original novel to Lana Wachowski, who became deeply interested in it. A year later, both Wachowski siblings wrote a first draft of the screenplay. Tom Tykwer, a friend of the Wachowskis, was invited to co-author several subsequent drafts with them in the following two years, constantly keeping in mind observations by the book's author himself, David Mitchell, while looking for international investors. In all those years, Portman was promised the role of Sonmi-451, but had to turn down the role at the last minute after becoming pregnant in 2010. However, she is given a special thanks in the closing credits.
The whole film was shot with two parallel filming units, one under the helm of Tom Tykwer and the other under the direction of Andy Wachowski and Lana Wachowski, sharing no crew members beside the cast and the directors themselves.
Because of the nature of casting on the film, the directors told the actors to think of their roles as a "genetic strain" rather than a series of individual parts, with actions in one story-line affecting another.
The film went through a series of troubles to land a financial backer, including studio Warner Brothers to pull out of financing the project as they didn't like the numbers. The directors had both waived their fees and started putting in their own money to keep the project afloat. Lana Wachowski credited Tom Hanks with helping get the film off the ground to the point where he inspired much of the cast and crew by being the first to fly to Berlin to begin shooting the film. According to Wachowski, Hanks was very enthusiastic about the project.
The character played by Amanda Walker is nursing-home resident "Veronica Costello," based on the popular song "Veronica" sung by Elvis Costello and written by Elvis Costello and Sir Paul McCartney, that song tells the story of a similar Veronica.
Vyvyan Ayrs' mansion in the 1936 plot-line shows up again as Aurora House where Timothy Cavendish becomes imprisoned in the 2012 plot-line. Jim Broadbent plays Vyvyan in 1936 and also Timothy Cavendish in 2012.
The trivia items below may give away important plot points.
The newly submitted manuscript that Timothy Cavendish is reviewing while riding the train is a Luisa Rey Mystery by Javier Gomez, the young boy that hangs around Rey's apartment and keeps telling her that her investigative assignments would make good mystery stories.
During the prison escape in Neo-Seoul, at the point when the plumbing truck is forced by the police to land, there is a sign visible on a building reading (in English) "Swannekke Atomic Power, Inc.", an apparent connection to the company running the nuclear power plant in 1973.
Vyvyan Ayrs (Jim Broadbent) comes into Robert Frobisher's room saying he's heard music in his dream from a violin. The music is, of course, the Cloud Atlas Sextet. In Neo Seoul, an old man (also Broadbent) is shown playing the Sextet on a violin.
Movie contains a spoiler for Soylent Green (1973): Timothy Cavendish says "soylent green is people" which is a reference to Sonmi 451's story in which old clones are recycled as food to feed new clones, and also to a science fiction film he had seen in the past where old people are 'recycled' into a new staple in the diet called the soylent green.
All cast members have several roles in the final film, spanning different times, races and even sexes. This was achieved through prosthetics, wardrobe and tight production times to switch actors between units. For instance, Halle Berry described the experience of filming as a Jewish woman in the 1930s under the direction of Tom Tykwer one day, then switching to an old tribal woman under the helm of Andy Wachowski and Lana Wachowski, and then again as a environmentalist in the 1970s, all in the same week.