Deliberate mistake: When the vortex is summoned to get rid of the monsters, other things get sucked into it. Cars, trees, light poles, other police officers. However other things or people who are more accessible do not get sucked in. For example, Phoebe hiding behind a bench, the bench itself, Phoebe's mother and a few cops hiding behind a cop car, etc.SAZOO1975
Continuity mistake: When fat kid is confronted by the Gillman and has picked up the shotgun, he looks inside and sees E.J. and another kid hiding behind the counter. Fat kid begs them to let him in. E.J. and the other kid shake their heads no and lower themselves behind the counter. A few seconds later, a distant shot shows the two shaking their heads and lowering themselves behind the counter again.SAZOO1975
Plot hole: The army showing up at the end of the movie is wrong on numerous levels. 1) Eugene wrote and sent out the letter that day. I find it hard to believe the mailed letter got to the army in just a few hours time. 2) How did the army know to show up at time square? When Eugene wrote the letter, nowhere did it say where to meet. Plus the boys didn't decide to go to time square until the last minute. 3) since when is the army deployed to battle monsters based on a letter that was written by a child?SAZOO1975
Other mistake: The werewolf gets blown to pieces by the dynamite, clothes and all. I can understand how the werewolf can reassemble his body as only silver can kill him. But how in the world do his clothes knit themselves back together?
Plot hole: In order to get rid of the monsters, Phoebe needs to read a text from Van Helsing's diary in order to summon the vortex. As Dracula approaches her, she becomes scared and misses on some words (the Scary German Guy is helping her read since she is 5 years old and she doesn't repeat some of the words he says). However the vortex still shows up to get rid of the monsters.SAZOO1975
Factual error: The way Horace was holding the shotgun was incorrect and dangerous; the kickback of the blast would have knocked him, like any other 12 year old child, off balance and caused him to miss his target.
Factual error: When the silver bullets are being cast, the silverware thrown into the melting pot appears to melt instantly, the bullets come fully cooled and hardened out of their mold in seconds, and are already fully formed and polished, straight out of the mold.
Other mistake: There is a lot happening at town square in the final scene; the kids are trying to get into the church, Rudy is killing vampires, and the German guy parked in front of the church. But in the overhead shot where we see the bat flying, there are no people or cars visible near the church at all.
Continuity mistake: When Wolfman throws one officer toward a car, the officer is shown leading with his left shoulder but in the next shot, which is a close up of impact, he hits with the right shoulder.
Plot hole: There are numerous problems with the final scenes in this movie. First, it's inconceivable that these kids are out at midnight at all; the boys are only 12 and two others are 5. Second, it took several minutes, possibly miles, to get from the house on Shadowbrook Road to town square, but the vampire mistresses make it there in mere seconds. Third, the sign in the store window where the two bullies are hiding said closed, so how did they get in? Fourth, Patrick grabs slack from the mummy's wrist but when the arrow pulls tight, he begins unraveling from the foot.