Michelle Williams (Blue Valentine) is Marilyn Monroe. Kenneth Branagh (Hamlet) is Sir Laurence Olivier. The film is a wispy fictionalization of the tense weeks the mismatched actors spent shooting the 1957 comedy The Prince and the Showgirl. Williams and Branagh occasionally hit high notes, but the tepid script is based on a couple of notoriously self-serving books by British filmmaker Colin Clark, who served as third assistant director on The Prince and the Showgirl. 99 minutes R.