During a dinner party, the hosts' two little kids entered the dining room totally n*de 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!"