I've got a good one:
8-9 years ago I was working for a big multi-national and was sent to California from London on a three month business trip.
Half-way through my stay they asked me if I wanted to return to London for a break of a week. That trip would have been in biz class as was the outward leg. Alternatively they said my g/friend could come over, but they'd pay cattle class only for her as she was not an employee of the company (but crucially had been previously).
On day of departure g/friend shows up at LHR - sorry Ma'am but flight is full. However, we see you have a corporate membership of BA Exec club so...you've been upgraded to Biz class (my gfriend 'forgot' to mention she was actually a student at that time).
On return trip she shows at SFO to be told, sorry Ma'am flight full, even in J/F class. But here's $600 dollars vouchers and a free cab back to the hotel. Day later gfriend returns to SFO and guess what...sorry Ma'am flight full, but... you're being upgraded to biz class..!
Later in the year gfriend exchanged voucher for buz class roundtrip LHR - Lisbon - MAD - LHR.
My boss at the time kept on reminding me at every opportunity what priviledge I had had of getting my gfriend to visit me for a free holidy, and what great expense they had incurred in paying for her flight.
I eventually told him the real story just before I left the Co., his face was green for quite sometime after...
Charles