Tony Scott asked for more money to film the rooftop scene in "Berlin" (in order to rent a helicopter for an aerial scene) but the producers refused. Scott believed that the scene was important and rented the helicopter with his own money.
The scene where Robert Redford's character asks Brad Pitt's character if he knew anybody in 'this apartment house' and tells him to be up on one of the balconies in five minutes is from a book by former Mossad agent Victor Ostrovsky who describes this test as part of the training of a Mossad agent.
On being introduced to Robert Redford, Omid Djalili joked "Mr. Redford, delighted to meet you - I loved you when you starred in Hawaii Five-O (1968). Without missing a beat Redford fired back "Well thanks, and I loved you in Doctor Zhivago (1965), although you have let yourself go since then."
Part of the film was originally set to have been filmed in Israel, but due to the sudden escalation of the Israeli-Palestinian conflict (in September-October 2000), and following the requirements of the actors' insurance companies, the filming took place in Morocco instead.
When the film was previewed in the summer of 2001, Brad Pitt said that it dealt with blow back from unsuccessful CIA operations and suggested that it might mean America had been the world's leading power for too long. However, after the 9/11 attacks, Pitt was quoted as saying the movie indicated that CIA operatives were needed "now more than ever".
Pitt had signed on for Ocean's Eleven which was due to commence directly after Christmas. Filming was hemmed in by Pitt's dates and Scott acknowledged there was a stopwatch on them all the time. Redford understood the pressures on Brad and he never complained.