Though she's from Korea originally herself, Ra Chapman (Kim Chang) doesn't speak much Korean. She's mentioned in interviews difficulty communicating with her birth father (who speaks very little English). She learned her Korean lines in this episode with a dialect coach.
Walford warder Steve Faulkner is a clear nod to Prisoner (1979)'s Steve Fawkner, who worked as a Wentworth officer during 1981-2.