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.
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.