Honestly I feel like I always project a little bit onto custom characters I make, and they kind of gain their own little personality in my head. Each character I've made in an MMO kind of feels like an individual OC I've made. I might not explicitly roleplay as the character by my actions in the game (especially if the game has limited options for actually RPing) but in my head I'm definitely getting the vibe of the character I made. Like the cutesy short one with pink hair and white eyes and bunny ears I made in Palworld gains a bubbly, sugary personality in my head. There's also been cases where I draw art of them or actually make them into OCs that survive outside of the game they were initially created for!