Guardians of the Galaxy Vol. 3 director James Gunn explained in an interview why viewers finally get to see Rocket (Bradley Cooper) become a hero in the final chapter of the Guardians trilogy. Gunn said that throughout all the movies, Rocket has never done anything heroic for anyone other than himself or his friends, but in the third movie, there is a moment where Rocket accepts himself and realizes that every life has purpose and is worthy of respect.
The film also delves deep into uncharted territory regarding Rocket's origins and his cybernetic alterations as an infant due to horrifying experiments. The film's overall darker tone aims to mature in its emotionality and shed light on animal experimentation and brutality in the real world.