Graffiti

Graffiti is found all over the five campaigns of Left 4 Dead, most commonly so within the safehouses. The graffiti is left be survivors who had been through the area, generally messages for loved ones, to other survivors, or simple comments, such is the case with the infamous Chicago Ted.

Easter Eggs

 * Many of the dates of death used to say "-Person- May 2008". When 2009 arrived, the death dates changed from 2008 to 2009.

Quotes

 * "NO ZOMBIE IS SAFE FROM CHICAGO TED"
 * "I miss the internet." (Argument in Dead Air Terminal Safe House.)