Sean Maher remembers reading for the part and liking the character of Simon Tam. He said it was Whedon's personality and vision that "sealed the deal" for him. For the role of Simon's sister, Whedon called in Summer Glau for an audition and test the same day. Glau had first worked for Whedon on an episode of "Angel". Two weeks later Whedon called her to tell her she had the part. This was Glau's first speaking role.