When Dane is spray painting Cheryl's name on the boulder, he's on the downside of the 'L' when he drops the paint can. As Jon is trying to rescue him from the boulder, the 'L' is complete. As Dane is trying to climb off of the boulder, only half of the downside of the 'L' is on the boulder. Later when they try to blow the boulder up, Cheryl's name is completely there.
Near the beginning, Jon and Punch are riding their bikes. Jon is clearly spotting a moustache and his hair under his helmet is on the long side. Just as he saves the kid from the truck on the freeway a few scenes later, his moustache is gone. A few scenes later back at the station, his hair is also considerably shorter. Later on, both the moustache and longer hair magically reappears.
The cars parked on the freeway by the truck before the car goes through the trailer are all inoperable junkers.
One car in the crash goes over another car and flips upside down. There is no-one at the wheel of that car when it's upside down.
The same red Chevrolet Caprice Classic station wagon appears several times, including on city streets and especially while the furs are stolen off the truck. This car appears in several episodes as well.