I’ve played a couple of stories where the writers have added a bunch of free question choices which you can ‘ask’ your character when they’re introduced. Putting in questions as simple as ‘What’s your favourite book’ for your MC to answer really helps paint a picture, and add personality to your MC —
[Sorry if that makes no sense]
As other people have said, adding in a well thought out backstory that will help playout how the MC acts in certain situations, is really important when giving a MC personality —
[try and go for a backstory with emotion, and maybe give the MC a problem they had to overcome in the past, one that would really affect who they are and how they act, in the present time. Avoid overused/cliche backstories/problems]
While browsing the web some time ago, I came across some lists which help when creating a MC
things that really help make them a strong and not flat character, and really help bring out their personality —
[I put the lists onto Google Doc, as they were too long to comment, I hope you don’t mind
]
14 Things to ‘Give’ your MC —
https://goo.gl/sRJGcL
6 Things to ‘Make’ your MC —
https://goo.gl/JfpQwp
13 Things to ‘Find’ for your MC —
https://goo.gl/HxBcLU
[ I understand some things on the lists won’t work with the kind of story you may be writing,
or just won’t work for Episode it’s self, but I really hope they help, even if it’s just a little bit !! ]
Something I find really helpful when trying to help find/show a character’s personality is taking personality quizzes/tests [MBTI] I searched around and found a few sites that are really good for this —
[Answering the questions the way you feel that your character would]
https://psychcentral.com/quizzes/personality/start.php
[Small example of this one here, showing my personality, I like how it gives a small paragraph explaining what I’m like, It really helps me to understand myself more, and It’s really very accurate]

Another site here —
http://www.humanmetrics.com/cgi-win/jtypes2.asp

This site gives a lot more detailed paragraphs about your personality —
Last site —
https://www.16personalities.com/free-personality-test
All these test/Quizzes take less than 10-15 minutes to do and are really simple to take —
[ I would really recommend taking them, and answering from your MC point of view, it helps a lot !! ]
I hope this helped some, and I wish you the best of luck on your story !! —
[ I would love if you could keep me updated on your story progress,
and would love even more to read it when it’s complete
]
