Though Pinky is a pig, he is still a very important character in A Day No Pigs Would Die. He is Robert's best friend and represents everything that Robert wants in a best friend—he is obedient, playful, and never makes Robert feel different or self-conscious.
Many of Robert's hopes and dreams rest on Pinky. Almost from the moment he gets her, Robert pictures Pinky as a brood sow, giving birth to hundreds of other pigs that the family can use for food and to pay off of their debt. When Pinky turns out to be barren, Robert's dream is shattered. It means that he will have to eventually kill his best friend so that the family will be able to eat, and it also seals his fate as a farmer. With Haven gone and no pigs from Pinky, Robert will have to give up school and resign himself to the life of a farmer in order to pay off the debt that the Pecks owe on their land.
The trial with Pinky also represents Robert's final rite of manhood. When Robert's father butchers Pinky, Robert comes to understand the inevitability of life and that being a man is about doing what needs to be done, no matter how hard it is.