The zombie virus is called VM2. V.M. are the initials of one of the writer's fiances.
The mention of an unseen character Kirkman is an homage to Robert Kirkman, creator of The Walking Dead.
One of the characters talks about being trapped in an S-Mart store, which is a nod to Army of Darkness where the main character Ash works at an S-Mart.
One of the characters discusses a zombie fight outside of Pittsburgh. Pittsburgh is the stomping grounds of modern zombie creator George A. Romero.
The zombie fighting characters were all originally going to wear masks or helmets when battling zombies, but that idea was abandoned as too impractical during filming. Because of this, the character Mack has a welder's mask clipped to his belt throughout the movie, even though he never wears it.