Originally, James McAvoy wanted to audition for the part of Michael until he auditioned with Steven Robertson and realized Robertson would be better at the part.
While researching and talking with people who have Duchenne muscular dystrophy, James McAvoy discovered that people who suffer from this disease would rather be ignored than pitied.
The original story was conceived by Irish writer Christian O'Reilly, inspired by his own experiences working at the Centre for Independent Living in Dublin where he worked closely with Dermot Walsh, a man who has cerebral palsy.
McAvoy was also in a wheelchair in X-Men