When McAvoy screen-tested for the role, he was initially rejected because the studio was seeking an actor with conventional Hollywood leading-man looks and physique.

He later recalled being considered the “runt of the litter” of those who tested, but ultimately got the role in late 2006 since the studio “wanted someone geeky”.  While shooting action scenes for the film, he suffered several injuries, including a twisted ankle and an injured knee, but the actor said he had a 'good time' doing the movie.