What is an example of allusion in the novel, Whittington?

The Lady refers to the famous story, The Fable of the Lion and the Rat, most notably recounted in Aesop's Fables, when discussing why Whittington and the other barn animals should enter into a truce with the rats. In the fable, a Lion traps a Rat and is about to kill and eat it, but the Rat pleads for his freedom, saying that one day, the Lion may need his help. The powerful and arrogant Lion doubts that that day will ever come, but lets the Rat go anyway. One day, however, the Lion is trapped in a net, and is only freed with the help of the Rat chewing through the ropes that make up the net. The events of this fable are enacted later in the narrative when the life of one of Whittington's children is saved by the leader of the rats chewing through the rope strangling her.