At the same multi-national a colleague who was moved to another office discovered he had been substantially over-payed (over $ 7000) in moving and relocation allowances.
He then tried to pay it back - he was eventually hauled in and told to "stop making trouble" by HR - of course 18 months later they came and demanded he pay it back INSTANTLY and suggested he had been totally dishonest.
Wisely he'd kept it separate and just wrote them a cheque - and quit for another company 3 weeks later. Did wonders for morale around the section