 They were joined by K-9 in "The Invisible Enemy", a robotic dog voiced by John Leeson and, on a few occasions; David Brierly.Jameson was replaced by Mary Tamm, who played Romana, a Time Lady and one of the Doctor's own species.Tamm stayed on for just one season before her character regenerated in "Destiny of the Daleks" and was portrayed by Lalla Ward.