Sometimes it involves customer deception.

A few years ago I was flying LAX/DFW on an MD80, I missed the upgrade and was in 21D.

A couple, maybe late 30s in age, comes in and takes 20E and 20F. I thought it funny that in June the woman was wearing a full coat.

She removed it, and I could plainly see that her arm was in a sling. The husband manuerved to block the view.

I debated to myself if I should tell the FA, and decided I needed to. As the FA came down the aisle, I caught her eye, and she gave me a nonverbal "give me a minute" cue. She then proceeded to tell the woman she must move. The couple did not resist.

After the couple was gone, the FA told me that she had seen the woman in the gate area; she thanked me. During meal service (I was a Plat then) she offered me a free drink - when I accepted, three vodka minis suddenly appeared. ^^^