A Quiet Day in Dodge - S18-E19
Other mistake: Festus returns from catfish fishing carrying a gunny sack full of fish that is bone dry when it should be dripping wet or at the minimum damp from the fish.
Mind Your Own Business - S1-E35
Other mistake: Ralph gives Ed the advice to try to "squeeze" his boss for a promotion, but gets fired instead. When Ed comes home, he first stops in to see Ralph but he's not home, just Alice. All he tells Alice is that he had words with his boss and got fired. No details. Ed leaves and Ralph comes home. Alice tells him Ed was fired and described in detail the whole story of him threatening his boss for the promotion. Ed never told her exactly why he was fired.