I seem to remember someone getting reprimanded for calling in fatigue-unfit (leave/pay taken away?), because a flight got changed from a local one to long-haul, and he/she wasn't rested for that.
I love how we are supposed to be rested for basically anything they can throw at us, and then change a split duty to continuous duty from 9 pm to 6 am, or short haul to long haul.
There are certain changes that you can't prepare for rest-wise. It's downright irresponsible of the airline to reprimand a pilot for calling unfit to keep the flight/passengers safe, just because it is 'legal'.