In an early scene where Darry is speeding to catch up to an RV in front of them, we hear the car shifting gears about three times. However, when shots looking into the car at Darry driving are shown, it is his right hand on the wheel, while we still hear gears shifting. Unless there was a shifter by the door and near his left hand or he switched rapidly, this wouldn't be possible.
In the scene where Darry is in the pipe and Trish is keeping watch, notices headlights coming, and runs to the car, you can clearly see her trying to shift the shifter on the floor, but when the shot of her through the window comes up, you can see the real shift on the steering wheel. In the next shot it is gone.
After Darry comes back from the pipe and has scared Trish, just before it cuts to the next scene there is a shot of Trish next to the window, on the window you can see spots of rain falling onto it. In the next shot while the two characters are driving away however, it is not raining, and the windows are completely dry.
When the Jenners pull up to the diner, only the left side stop lights light up (red). When the Creeper attacks the police behind them later and they brake, both sides light up; the driver's-side stop lights light white and the passenger-side lights light red.
In the very beginning of the movie, when Darry first says the name 'Poli-Sci-Track-Team-Guy', and right before Trish tells him that her relationship is none of his business, Darry's facial expression changes quickly. When Darry says 'Poli-Sci-Track-Team-Guy', he is smiling. Then, it cuts to the side of Darry's face, and he is not smiling.
As Patricia and Darry drive by the house and see the Creeper dumping bodies, as he tears out onto the the road to chase them, you can clearly see a truck with its headlights on down the road behind the Creeper vehicle as it cuts across the grass to enter the road.
After sliding down the pipe on his front side, Darry would not have landed on his back falling flatly as shown. He would have either landed on his chest, landed head first, or on his back rotating as he landed.
When Darry and Trish drive up to the diner, there are only a couple of vehicles in the parking lot. When they get inside the diner is completely full, 30-40 people. However, since it's a small town, they could have walked or car-pooled.
Justin Long played the Creeper in the very final scene, where we see that his characters eyes have been eaten. Though it is true that Breck played the creeper in every other scene, it is Long's feet that are visible in the final scene as the monster works at his bench.