It's just a dog being cool. That's the movie.Edit
There isn't much resembling a plot. Cool dog just does cool things for the whole movie, like saving kids and pilots who pass out after a "safe landing" that involves a lot of fire.
He beats up a gratuitous animal control officer.Edit
Cool Dog literally puts that joker in the trash. He is then put in a fucking dump truck as people either ignore him or laugh. Including the people putting him in. This is the penalty for defying the cool dog.
-Cool Dog is Alucard spelt backwards