Supply Sergeants Never Die - S2-E6
Continuity mistake: The Supply Sergeant Singer's second shirt button is buttoned as he approaches the counter, but as he continues around the counter it's not, then it's buttoned up again. (00:25:00)
Continuity mistake: While Gomer shows a little girl how to play jacks with sugar cubes, the number of sugar cubes go from 4 to 6 while the girl plays. (00:10:00)
Answer: If you saw the whole series run, you know that Gomer was a country bumpkin. He fumbled, stumbled and tumbled his way into one disaster after another. There was an episode that questioned why he was never promoted. However, a few years before Jim Nabors died, the real Marine Corps, gave him a ceremonial promotion to the rank of Lance Corporal, which Jim gladly accepted.
Unfortunately, I never saw all the episodes. Only a few episodes and a clip of the episode where he sings "The Impossible Dream" which made me wonder why he was still a PFC. Thanks so much for the info.