Mendes insisted on two weeks of cast rehearsals , although the sessions were not as formal as he was used to in the theater , and the actors could not be present at every one . Several improvisations and suggestions by the actors were incorporated into the script . An early scene showing the Burnhams leaving home for work was inserted later on to show the low point that Carolyn and Lester 's relationship had reached . Spacey and Bening worked to create a sense of the love that Lester and Carolyn once had for one another ; for example , the scene in which Lester almost seduces Carolyn after the pair argues over Lester 's buying a car was originally " strictly contentious " .