I liked the dog with hard work tied to his back. I thought him being the normal guy, going to work every day, to do a boring job just to fullfill his dreams. And every day he says to himslef today I will do sometinhg great, something extraordinary.
As he opposed the grey dogs you lost me. I just thought "what?!"
The octupus looked kinda cute.
In the end I think he wanted to break free, he wanted to be a octupus. And he finally become one, floating free, apart from the other dogs which follow their normal grey day life.
Given the little interaction you could have, this would maybe better be a movie. There are movies here that have more interaction.