Pre-9/11, had a boarding pass from one segment, however no ticket stup (before etickets as we know today), was about to board and was pulled aside, GA or supervisor looked at me, typed something and said to the effect, "ah, Mr. Hooverer, not a problem, we will clear it up, please go ahead and take your usual seat and have a nice..."
Another, e-tickets were new, a GA could not find my reservation reservation, remembering what another GA had told me recently, mentioned a cryptic code + WP number + something else, and everything for my reservation came up including upgrade and all was well, needless to say, had to explain how I new the commands.
Another, similar to above however on DL, an agent had told me how to "hook" or when to mention the term to a GA, it worked, ah, the days before e-tickets as we know now.
On-board, woke up from a power nap to find white linen towel on my right shoulder as I was in the shakespere set, realizing that I may have been snoring and the FAs were concerned about my nap, after getting up and going to rest room to freshen up, saw the FA in FC sitting in 1B on break, went to gally and poured and served the FA Coffee as well as a few others in the near empty front cabin.
-H