20 Things You Didn't Know About Serenity
7. Summer Glau Struggled To Finish Her Scene Because Of Sean Maher's Acting
Whedon states that the most difficult scene to shoot was the scene where Simon has been shot, and River is left distraught.
Sean Maher's acting proved to be so good, that it appeared so real to Summer Glau, and, as they had grown so close during filming, Summer couldn't keep it together.
She apparently kept crying, and they struggled to get the scene finished.