In the warehouse, when the group is searching the RV for the missing dead body, you can hear a TV report in the background. The report is taken directly from George A. Romero's Night of the Living Dead (1968), shot nearly 40 years before this film.
Begins on the same day as Night of the Living Dead (1968), although the setting has been updated to the present day. The concept for the film evolved from an idea that director George A. Romero had earlier for a "Living Dead" TV series, which also would have begun on the same day as "Night of the Living Dead."
In the scene with the zombie doctors, a voice can be heard on the radio inviting people to aim for the head. This is the voice of Tom Savini, a longtime friend of George A. Romero. In fact, this audio is lifted directly from the bonus features of the remake of Dawn of the Dead.