A Delicious Prank

Long ago, in my early twenties I worked at a variety of restaurants.  For posterity's sake, the list is
Tammany Hall (Salem, MA)
The Sandbar (Marblehead, MA) and
The Courthouse Deli (Salem, MA)
Anyhow, at the Sandbar the sous chef was this big intimidating looking guy--for some reason the Indian dude from Predator comes to mind.  Anyhow, when a new waitress would come on board, he always had some ugly and mean-spirited prank to pull.  The one I remember best goes something like this...
You need an accomplice that is friendly to slip into conversation with the new person that the 'bad guy' in the prank's brother was an Olympic swimmer--depending on the locale and perceived intelligence of your victim, you may want to tone it down to 'great high school swimmer' or something like that.  But the point is that you need to get the victim to approach the 'bad guy' in conversation and get them to ask about their brother.  You score the most points if you can get them to ask in a group setting 'So Bob, I heard your brother was an Olympic swimmer'.  If you have a good bad guy, without blowing it, the bad guy has to go totally morose and say 'Where did you hear that?  My brother drowned last summer.'  and then just storm off.

That's it.  Likely it never gets brought up again and you've totally made someone feel terrible, but it is a hell of a prank.