As for my experiences:

1) Two smelly, grubby, female backpackers plonked themselves down in Premium Laurel (C class) on EVA's 777 at Bangkok bound for London. Loads of bags, loads of attitude.

Cabin crew offered welcome drink and they asked for a "bottle of house red". "One moment please." Cabin was rather busy with boarding pax passing through. Moments later they jabbed the "call attendant" button and said "if you can't do the wine now can we at least have some juice, we've had a long day". Nothing was delivered. Once boarding was finished, the purser appeared and asked them their names which they gave. They weren't on the printout, so the purser politely asked for the boarding passes which they proudly presented. They had economy seats and were sitting 2 classes up. When the purser asked them to move they replied "No way, its too late now - we've already got comfortable. We don't want to sit back there, its packed out. Its a long flight, you know" Purser points out the door is still open - and that she'll ask BKK security to remove them if they don't move rightaway. They moved.

2) Husband flying with wife in economy. Had spotted his mistress several rows ahead in the same cabin. Asked the purser to upgrade the mistress to avoid trouble. She agreed.