(at around 55 mins) After devouring a security guard's brain, a zombie picks up a phone the guard had been speaking into and says "Send more security guards!" This pays direct homage to the original The Return of the Living Dead (1985), in which a zombie who had been devouring a paramedic picks up the radio in the ambulance and says "Send more paramedics."
Both this film and the next entry Return of the Living Dead: Rave to the Grave (2005) stray away from the series' rules that the Trioxin zombies are no longer the indestructible juggernauts of the first movie three movies, but instead much weaker and sometimes are seen to be dispatched with no more than a few body gun shots. Prior to this film, nothing short of incineration or electrocution with extreme high voltage would destroy a Trioxin zombie.
The trivia item below may give away important plot points.
Jana Kramer was originally supposed to reprise her role as Katie Williams in the next installment _Return of the Living Dead: Rave to the Grave (2005)_ which was filmed back-to-back with this film but Kramer suffered a serious gallbladder infection and could not appear. Her character, who was scripted to survive the film, was then abruptly killed off and replaced with the character of Jenny in the next film.