Douglas explained, “I had to cough a lot in ‘Gunfight at the O.K. Corral,’ and I had to choreograph every cough. Since movies are not shot in sequence, I had to plan where I was going to cough, how lightly or deeply, and where I was going to have an attack. In some scenes, I didn’t cough at all. [...] A movie is not real. You create the illusion you want to create."