Christopher Walken's character says "It reminds me of a time when I was in Vietnam with a prostitute", when he speaks to Marcus about babies crying. This is yet again a scene in which Walken himself was in in the film "The Deer Hunter".
The subway chase at the end between Marcus and Terry is a direct reference to the one at the end of Christopher Walken's "King of New York", who is a cast member in the game.