Stave 3- How did Scrooge become the punch-line of the Yes and No game at Scrooge's nephew’s house?

It was a game called Yes and No, where Scrooge’s nephew had to think of something, and the rest must find out what, he only answering to their questions yes or no, as the case was. They bring up a growling animal. Finally one of the girls says, “I have found it out! I know what it is, Fred! I know what it is!” “What is it?” cried Fred. “It’s your uncle Scro-o-o-oge!”