The Platter Bum is the individual who went ahead and ordered an expencive dish (thus distinguishing thereself by putting on airs as the rich guy) but does not share. Others in the party will notice and feel slightly annoyed.
Then when everyone is served, the Platter bum then askes others around them if they could try a sample of what others are eating in order to "see if they like it."
Others will feel compelled to be polite and offer the morsel to the Platter Bum while they secretly resent the fact that they have only a small meal to satisfy themself with while the Platter Bum has a frigg'n buffet, half untouched in front of them.
NOTE: The Platter Bum usualy never finishes their meal and leaves most of their food to be wasted. This also will piss off company who may still be hungry or may have been the one treating the group to the meal.
Relative 1 : "Jeez! Would ya look at that pig!"
Relative 2 : "Huh? Who ya talkin about?"
Relative 1 : "That uppity cousine from the country. He found out dad was paying and he ordered the most expensive steak on the menu."
Relative 2 : "That little turd! All I had was a grilled chicken salid."
Relative 1 : "Yeah, and he's been begging food bites from everyone around him and hasn't touched his own plate. What's he doing? Saving it for later?"
Relative 2 : "I agree. He's being a real Platter Bum tonight. Dad aught to tell him off and not pay for his meal."