I'll always remember an anecdote Hugh Laurie told a few years ago.
He was invited to John le Carre's birthday celebration at a fancy restaurant in London. During the meal, one of the waiters pulled him aside to make a request... Apparently the restaurant had a tradition of surprising any birthday celebrations with a cake, and since they knew Hugh was a piano player, they asked if he wanted to play "Happy Birthday" when it was about to come out.
Of course, they didn't actually tell anyone there that part of the trick was that shortly after the music started they'd switch the lights out briefly as the cake with candles emerged from the kitchens.
What had slipped the restaurants mind, was that a large portion of the guests attending happened to be senior members of assorted Embassies - French, German, USA, even Russian (*cough* Intelligence Agencies *cough*) and all their bodyguards. Armed bodyguards.
Hugh starts playing. He can see the door to the kitchen open, the cake appears, the lights go off...
Lots of startled sounds. When the lights switch back on, a portion of the guests are under the tables and another portion are standing there with pistols in hand and some rather surprised waitstaff are holding a trolley with the cake.