Piggy (2012), directed by Kieron Hawkes, is a complex psychological and emotional undertaking. Although IMDB ratings appear quite low, I believe that they misunderstood the intent, or the purpose of this film. From my knowledge and experience, I've come to see movies of this psychological complexity having multiple vantage points, or perspectives.
There are quite a few ways you can look at this film: 1) from the view of Joe, 2) Piggy and/or 3) from the historical track record of Joe and what it means in respect to Piggy's sudden appearance. I don't intend to ruin the movie for you, and it's never been my intention to begin with to spoil it, but you'll know exactly what I mean when you watch it.
Sometimes I wonder if the director was referring to the Piggy from William Golding's novel Lord of the Flies (1954). This book basically describes a microscopic world of children stranded on an island, desparately seeking an order to unify them to a single cause: to find a way off the island and establish as much order as possible.
Piggy's intellect benefits the group only through Ralph; he acts as Ralph's adviser. He cannot be the leader himself because he lacks leadership qualities and has no rapport with the other boys. Piggy relies on the power of social convention. He believes that holding the conch gives him the right to be heard. He believes that upholding social conventions produces results. Read more about Piggy here on the Wikipedia Entry
Interestingly, the Piggy we know in this film portrays something similar to the Piggy we see in Lord of the Flies. Both Piggies are interested in reinforcing an order, based solely on social conventions, except in Golding's version we find a more positive, less violent approach.
Despite his violent urge, Piggy is seeking a justice that is, in a way, perverse. Justice means standing up for the idea of justice, not typically justice in terms of what we understand. The reason why I am unsure whether he actually exists or not, or if it's primarily based on Joe's perspective, is that of his sudden appearance as a consequence of Joe's brother's death and his subsequent sudden appearance.
Joe led a routine-based life: wake up, go to work, do drugs, and sleep. Pretty average and normal life for Joe, except when his brother dies and then I think that is when he begins to blur the world of reality and imaginary. It's hard to believe that Piggy is real, even though he teaches Joe how to stand up for himself.
My question is this: after learning of his brother's death, did he flip and become Piggy? Is Piggy a manifestation or does he really exist? Watch the movie and find out, maybe you'll have a totally different take on it!