Dìdi, Mulan’s dog, is something of a sore point in the family.  The Huas have always had a farm dog, but Dìdi’s predecessor came home when Mulan was not quite four, and she began to call it her dìdi (Little Brother).  It, and its replacement of one year (which is the dog we see in the movie), have both been more interested in following Mulan around from chore to chore than in doing any work of their own.  Hua Zhou laughs and says that the dog really is her dìdi, but he is never able to find it completely amusing that he and his wife had no sons.