Warren and Goober are eating at the diner, which is full of people, before going to Andy's house to warn him about the picnic. Andy was awakened, claiming it was the middle of the night. Mayberry would not have a 24-hour diner.
Right after Andy and Helen drive off in the pick up truck, a microphone can be seen briefly in the bottom left corner of the screen.
When Andy borrows Goober's truck after the squad car had been sabotaged, he puts the picnic basket and cooler in the back of the truck. But, forgets to shut the tail gate before driving off.
Just a couple of episodes earlier an irritated Andy admits to Goober that he knows nothing about cars. Yet here, as the hood of the squad car is raised, he instantly points out that the distributor cap is missing.