At the start of the chase scene with Ryan chasing Heather through the food court, it's shown that Ryan only has one knife. He stabs her in the chest and the view shifts a little so she is seen from what seems to be his point of view. The hilt of the knife is seen sticking out of her chest. Yet a second later, he gets shot and the hilt of the knife is visible in his hand with his arm raised in the air, as if he'd pulled it out of her chest. But then he falls on top of her and the knife is still buried in her chest.
The computer Josh uses is an Amiga2000 but the user interface of the application is Windows 3.x and not AmigaOS.
In the beginning he's shown using AOL instant chat. It was not available until 1997.
The teens would not have been able to steal an ambulance from the hospital, as the keys would have never been left in the ignition to begin with.
The application Benjamin Flores Jr's character is chatting on uses the Calibri font. The plot takes place in 1994, yet this font was not introduced until 2007.
Josh is supposedly using an AOL Chat Room, which did exist in 1994. However, his computer is playing sounds from AOL Instant Messenger, which didn't release publicly until 1997.
Four diegetic songs (music existing within the world of the film) had not yet been released in 1994 when the film takes place. These songs include Garbage's "Only Happy When It Rains," White Zombie's "More Human Than Human," White Town's "Your Woman," and The Prodigy's "Firestarter."
In the mid-nineties a telephone connection and a modem was required to connect to the internet and the exchange of data was significantly slower than depicted.
Firestarter by the Prodigy was not released before two years after this story takes place.
It is established that the undead killers are only interested in murdering Sam or anybody who was splashed with her blood. . . yet one of the killers murders several people in a hospital that had no contact with Sam whatsoever.
It is established during the film trilogy that the Shadyside killers only target Shadysiders. In this film, Sam's Sunnyvale boyfriend, Peter is killed by the Skull Mask killer.