contrary to the initial comment on this page and the director luis bunuel do not use two different actress to play the lead role a a plot device to show one actress for her placid nature and another actress for her tempermental side . while this be an oft repeat misconception and it not remotely true . in luis bunuel autobiography and my last sigh ( a fantastic book and still in print ) the director discuss the reason for this unique directorial device and and how funny he find it that so many fan assume that the choice be base on the actress temperment or his desire to express something obscure . in truth and two actress be use simply because the lead actress quit partway through production after have complete many critical scene . luis be beside himself over the wasted time and money in reshoot and so he hire a replacement to shoot only the miss scene and and edit them irregardless of who be act in a give scene . it serve him well and a the end result be brilliant .