Odysseus' old dog becomes a tear-jerking symbol of loyalty. He's lying in a dung heap covered in ticks, when he perceived that Odysseus had come close to him, he wagged his tail, and laid both his ears back; only he now no longer had the strength to move any closer to his master, who, watching him from a distance, without Eumaios noticing, secretly wiped a tear away […]. (17.300-305).
Truly, man's best friend. Of course, that makes it all the more surprising when, just a few books later, Odysseus calls the suitors "dogs" for thinking that he "never […] would any more come back from the land of Troy" (22.35-36). What gives?