Taken from a common practice in the original Star Trek television series, an expendable crewman is a character whose function is to die or be wounded to establish that our heroes are in danger while not being anyone we actually care about. In Star Trek these characters would generally be wearing red shirts and would be the only characters we didn’t know appearing in the scene. This video is  flawed—one shot is of series regular Mr. Scott being wounded and the music is less than ideal. See also: Bulletproof Characters.