The screenplay for the Joss Whedon film is expected to be finished by the end of 2006, the New York Post reported Wednesday.
McPhee's summer has already been full of surprises as she fractured her foot and dealt with bronchitis and laryngitis, which delayed her start on the "Idol" tour.
Director Ron Howard's daughter, Bryce Howard, was a reported favorite for the role but she's since corrected those reports.
"I don't how I'd look in that suit," Howard said.
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