Left 4 Dead 2, released by Valve in 2009, follows four survivors fighting through zombie hordes, and Nick is the sharp-tongued con man of the group. The Boomer is a bloated special infected that vomits on survivors to attract a horde, so its callout became a familiar warning for players. Short clips of survivor voice lines circulated on fan soundboards and in gameplay edits, where the one-second warning was easy to reuse. It remains popular because it is instantly recognisable to Left 4 Dead fans and still reads clearly as a danger signal to newcomers.