I have sooooo much fun with character design!! In my practice comic, I honestly just tried to think up characters I hadn't seen before but figured I'd enjoy drawing.
First, Miss Khan. I think a few months before making up the characters, I'd seen an article in some Tumblr/twitter feed about chubby Asian ladies. The idea stayed in my brain because I'd honestly never considered that a possibility before. When I decided I wanted a lady at the head of the story, I remembered that article. Later when I started coloring her, I gave her a darker complexion, yet again because that was something I'd not seen before. She is super fun to draw, so I'm very satisfied with my choices. I always put her in soft/comfy looking clothes, because she's very casual and I like her to look… psh, IDK, approachable? or something.
For Matt and Stan first I decided they were going to be cousins (why? you guessed it--- because that was something I didn't see much in comics). After that, it was pretty easy to decide what they'd look like. I started with Matt— I wanted him to be a traditional brodude. he's decked out in sports emblems, looks potentially threatening, makes finger guns at everything, really just a poster child white dude. Tbh the beard was because he's a pirate and pirates should have beards. Once I had Matt down, I just made Stan THE COMPLETE OPPOSITE. Tiny, effeminate, black, terrific posture, doesn't have a problem with emoting.
But while I wanted them to initially come across like total opposites, I wanted them to eventually seem more and more similar, so I tried to give them obscure parallels. They use different facial expressions but have the same facial features. They use the same hand motions and neither has a sense of personal space. They both always dress very nicely and frequently worry about their appearance, even though their styles are totally different. They're Drama Queens.

Finally, with Ekat I just wanted an somewhat older lady who could totally beat someone up. There's a lady in my church that I based her physique off of. I'd never tried to draw a woman with right angles in her face. Honestly the hardest thing about her was deciding what I wanted her hair to look like: I knew I wanted it to be long and grey, but there's a loooot of different types of grey hair. I drew her for well over 2 years and changed her hair every other week before meeting a lady with wavy, dark-streaked grey hair and thinking YES. THAT'S EKAT.
TL;DR: I literally just picked random stuff I didn't see often in comics.