John Leeson has been the primary voice actor for K9 since his introduction, although two other actors have voiced the character. David Brierley voiced K9 during Season 17 after Leeson chose not to return to the series (Leeson subsequently signed up again for Season 18), and Roy Skelton, better known for his work voicing Daleks, voiced the character in TV: Destiny of the Daleks when all was required of K9 was a croaking sound due to the character contracting a form of robot laryngitis.