I just want to mention something before I talk about how I make my characters... When you guys say realistic, do you mean their aesthetics, characteristics, or personality? I personally don't like to say that my characters are realistic or unrealistic. There's just too much to consider that could make a character both of those things. Now, what I like to consider my characters to be is fantasy, due to the realm that they live in. They are both realistic and unrealistic to me because 1) they are unrealistic due to the fact it's fantasy, but 2) they're also realistic since they follow the laws of the realm they're from (like laws of nature and whatnot) and their personality and characteristics are believable. If you think about it, your "realistic" animal characters are still unrealistic because they're humanized, if you are comparing them to real animals. Now, don't take this as me being rude or anything, I'm just trying to point something out. I don't really understand why anyone claims that their chatacers are realistic or unrealistic.
Okay. Onto how I make my characters. Just a side note, this is how I design characters in general, not just for this game. Most of my characters are human, btw. And I'm more of a novel writer than a roleplayer.
I actually grew up designing new characters day after day. I have so many that it's not even funny. I don't know where the inspiration came from to make all of them. Back then about 10 years ago, I mostly just had a vague image of what they looked like in my head, drew them, and then based their personality and characteristics off of the vibe that they game me. After that I would make relationship ties between them and my other characters.
Sometimes, however, I created characters specifically to fill roles that I needed in my stories. Such as the antagonist, specific people to get the story rolling in the direction I needed it to, and etc. I didn't go too deep into this other process back then until I really started to get a hold of the plotlines. Their personalities had to follow their roles enough to make the choices that I wanted, but the fun part is figuring out WHY they make those choices. Why are they like that? Why did they choose that?
I have a thing for back stories. All my characters have one that back up their mind set. A large portion of their personality, however, is free reign for uniqueness. Multiple characters who go through the same back story will act differently. Personality + backstory = a unique character. Because of that formula, it is quite difficult when you're trying to design a character to fit a specific role that is a key to the plot without any plot holes showing up. So, sometimes I allow the plot to change or evolve around the characters to avoid holes, as long as it doesn't change the main idea that I'm trying to achive in my story.
It's a very tedious process, to be honest. I have been developing specific characters for over 10 years now, trying to refine them to their best potential. I think about a lot of things when trying to refine them. Not only do you have to think about who you want them to be when the story begins, you have to think about who they will become by the end. Character developement throughout the story is one of the keys to keep it interesting among readers, and also increases the readers' ability to relate to the characters (although a huge chuck of a character being relatable comes with the personality + characteristics + backstory equation, which needs to be balanced enough to be believable because a believable character is also a relatable character).
Anyway. When I create characters based on roles like this, I end up designing their personality and characteristics first, then their aesthetics based on those two things, and finally their backstory to connect the role and personality. I may also change their aesthetics a little after I figure out their back story, like maybe I decided they got into some terrible accident in their past and have scars from it. Their aesthetics may also change as the story goes from certain events, which is always fun. Some of the many things I do to or give my characters as the story goes that changes the way they look are cuts, burns, loss of limbs, curses, and etc. I'm so brutal... But it has to be done. Because I said so. I know, I'm terrible. Or I'll just throw in the excuse that nobody would know paradise without knowing hell first. Heh.
Hmm... I'm wondering if my post might be a little confusing. Maybe I should conclude by saying that my characters are not set in stone and stay the same as the story plays. I design them with a timeline and change them as it goes on. I like to consider character designing an art because of how complicated it can get. To be honest, I think designing characters and their back stories is the best part of creating a story. I mean, what is a story without characters? Their design is essencial.