I was recently on a AKL-HKG flight and was upgraded to business. Passenger next to me was student on her way back to HK to see her parents for the holidays. Assumed she had rich parents but about half an hour before the end of the flight the cabin crew all gathered round, gave her a box of chocolates and wished her 'happy birthday'. it was very sweet of them.

I assume my neighbour had received a birthday upgrade. A couple of years ago it happened to me too (no chocolates but one of the most expensive birthday presents I've had).