The handlebars on Bill's motorcycle repeatedly change between shots (standard vs. apehanger).
At the end of the episode "Hog Wild", Bill and Ralph drive down the road in their car. To the left of the screen, you can see a major highway going in the same direction as they are going, even though they are leaving a town in the middle of nowhere, and the highway does not appear in any other shots.
When Ralph & Bill are attacked by the bikers, Bill's Badge is stolen by Preacher, the burly leader. Once Preacher pins the badge on his jacket a close up shot is made. The badge is an oval shaped security guard badge that says "Special Officer" rather than a DOJ FBI badge.
When Ralph prevents the Sheriff from driving away by tearing the driver's door off of the Police car, you see that the Sheriff is wearing dark pants or jeans with an untucked shirt. When the Sheriff exits the car he is wearing tan khakis with his shirt tucked in.
You see that the Road Hogs have already smashed up Red's Gas Station but when you see Ralph flying by it twice it's completely undamaged.
When the biker is trying to fly with Ralph's suit the 1/USA tattoo on Preacher's chest has faded/partially worn off. In the next scene the color is more vibrant again. This happens several times in the episode.
Before Ralph prevents the Sheriff from fleeing, the emergency lights atop the Sheriff's car are on. However when Ralph stops the Sheriff from leaving, the emergency lights are now off .
When Ralph is forced to hijack the Tractor Trailer Truck and is arguing with Preacher before they both get into the truck, another camera shot shows a different badge affixed to Preacher's jacket. This badge seems to be more reflective of an FBI badge.