When Ben and Darren walk over to Wolfgang's house, Ben is wearing brown corduroy pants. Then when they go down to the basement, he's wearing blue jeans for a few shots. And then he's back to wearing his brown corduroys for the rest of the scene.
During the hill scene, Wolfgang creates 2 holes in the ground. One leading downward while the other ends going up exploding a large hole near Darren and Ben.
At the end of the film they are back at the same hill and there is no sign of the hole near the tree trunk Wolgang came out of.
At 07:16 on the DVD, "2517 Davana County School District" is written on the side of the school bus, but at 49:58, the sheriff's helicopter lands by a sign reading "Davanna County" and at 50:51, deputy Gordon reads a copy of the "Davanna County Gazette".
During the maiden voyage of the Thunder Road, Wolfgang removes his glasses and puts them in his jacket/shirt pocket before putting on his gas mask. After putting on the mask his glasses are back on underneath it and he is not seen putting them on.
On the maiden voyage of the Thunder Road, right after the sphere-field activates, the camera cuts to the front of the ship for a brief second and a half, and we can see the boys, mainly River Phoenix in the middle, waving their hands very enthusiastically and out of character for the scene. It's possible that this was an outtake that was cut into the film by mistake. Joe Dante has always said that due to studio pressure, the film released is basically a rough cut.