In the game of "Yes and No" that the guests played at Fred's party, who did the "disagreeable animal" turn out to be?

The guests at Fred's party play several games, including one that resembles modern day tag.  They end with a game of "Yes and No," which is a clue-based guessing game along the lines of Twenty Questions.  Scrooge and the Ghost of Christmas Present watch as Fred describes a truly disagreeable animal.  They come to find out that Fred has been describing Scrooge himself.

It might be tempting for the reader to think this an unkind move on Fred's part, but Fred follows it up by drinking to his uncle's good health.  When the reader further considers that Fred invited Scrooge to the party, the reader can better tolerate what might otherwise be seen as a character flaw on Fred's part.  We see, in the end, that although Scrooge is not present, Fred's game is not intended as malicious.