>>149316607In the movies, we see that they:
1) Fear death, scream, call for help;
2) Talk to each other, smile, articulate in the background;
3) Help the wounded on the battlefield, other clones pay attention to the wounded and can get distracted from a firefight;
4) They are good friends with the Jedi, psychic mind readers, who trust them absolutely, are comfortable around them, and are not afraid to turn their back to them, have banter with them. So that means they are not some kind of evil psychopaths, who dream of killing them in front of their faces, because otherwise the Jedi would not trust them ever, and Obi-Wan would not be a friend with someone like that.
5) Have customized armor, various emblems on their helmets, starfighters.
Everything was there in Episode III. Lucas merely elaborated on that in Clone Wars, went far more in-depth than a movie would let him due to time and story constraints, and spend significantly more time on that over the course of many seasons.