 According to the commentary on Season 1 Episode 5, the scene in  which Jim is hit in the face by Roy was an accident and real. David  Denman (Roy) backed into John Krasinski (Jim), and hit him in the  face, resulting in John bleeding. The cameras kept rolling and they  kept the shot in the show. But, as a result of the injury, a photo  shoot scheduled for the next day had to be canceled because Johns  lip was so swollen.