Complex sentence: The role of Mary Alice was originally given to Sheryl Lee, who portrayed the character in the original pilot that was filmed for ABC, but Lee was soon replaced by Strong after Cherry and the producers thought Lee was not right for the part.
Split into simpler sentences: The role of Mary Alice was originally given to Sheryl Lee. A pilot was filmed including Lee, but Brenda Strong eventually took over the role, as producers thought that Lee was not right for the part.