Redshirts

'Redshirt(s)' is a slang term for a fictional character/characters in a film/book/tv show who will obviously be killed off quickly and without undue fuss in order to further the plot. Examples include various horror fiction stereotypes, as well as policemen and other interchangeable figures in other fiction

Origin
The term first saw useage among fans of the sci-fi show Star Trek, in which the protagonist security forces wore red uniforms. This security force maintained an extrodinarily high on-screen mortality rate; the death of a reshirt or two being the writer's plot device of choice to indicate danger or raise dramatic tension. The term has since risen to a generic status, and may be used concerning any form of fiction.