Draw your OCs in a way that tells some sort of narrative. Not too inside baseball type of deep lore but find a balance where even a new audience can follow it. Comedy or sex appeal seem to work best on twitter. Serious and dramatic can work too but they gotta be entertaining.
From my own experience:
Creating characters are meaningless until you make the world where they are situated in to ground them! An OC is just a design until a story is written,until the setting is developed. Make people ask ‘what why where? And most importantly.. “What’s next?”