While the documentary is only 12 minutes long, it covers aspects like designing for NPCs to reflect their values (complete with feedback and interactions with the writing team) as well as drawing inspiration from outside sources and collecting feedback. It’s not as simple as just pulling together pieces from an existing template, either; there are always new elements to consider and an overall aesthetic to keep congruous. Check out the whole thing just below for a look at what goes into keeping your Jedi in setting-appropriate gear instead of hot pink overalls.
Source: YouTube; thanks to Swtorista for the tip!