An example is detailed in Graham McCann's behind-the-scenes biography of the show. A BBC executive recounts stopping by to watch a taping of the show in its first season, and initially finding it utterly baffling and unfunny. He then admits that it all immediately clicked together and became hilarious once he realized that Mainwaring was the Captain and Wilson was the Sergeant, rather than the other way around as he'd previously thought and as would initially seem to be the case when looking at the characters at first glance.
Or perhaps, more accurately, Fridge Tearjerker: in the prologue that opens the first episode, we are given a quick glimpse of all the members of the platoon at the then-present day of 1968... with the notable exception of Corporal Jones. Heavily implied to be the oldest member of the platoon at the time of the war, in the roughly twenty-eight years since he has almost certainly passed away.