 In some scenes, Sullivan as Sam Asgarde bares his teeth as he faces  the enemy and/or fires his weapon. Consultant Walter Suarez, who was  a Vietnam veteran, advised Sullivan not to show his teeth, because  soldiers use camouflaging face paint and mud for a reason: to be  inconspicuous. A soldier should never show bared teeth, their  whiteness can make him a target. Sullivan decided to go for the  drama rather than the realism.