During a dinner party, the hosts' two little kids entered the dining room totally nude and walked slowly around the table.
The parents were so embarrassed that they pretended nothing was happening and kept the conversation going.
The guests co-operated and also continued as if nothing extraordinary was happening. After going all the way around the room, the children left.
As they disappeared out of sight, there was a moment of silence at the table, during which one child was heard to say, "You see, it is Vanishing cream!"