I've been rewatching 'The Expanse' lately.

Cara Gee is phenomenal.

She was originally cast as just an assistant to Fred Johnson.

The showrunners noticed that she was delivering her lines very clunkily. But then they heard her deliver her lines in 'Belter Creole' very sing-song like.

And then they realized that she was reading her English lines like they were her character's second language.

She basically became a main character after that.