I know of a case from a few years back - JFK to LHR with BA.
The Y section was full, which included a late arriving circumference challenged gentlemen. He sat down and straight away protested that due to lack of space on the busy flight there was insufficient room for him and so he should be upgraded to J.
After some amount of protesting the crew resolved the situation by upgrading the passengers to either side of Mr.Whinge, whilst leaving him to his Y class seat. He had no legitimate cause for complaint and the crew made sure he got no more than he had paid for.
Perhaps his obnoxious attitude had yielded results for him on previous flights though...