The Master uses Kamelion, a shape-shifting robot, to pose as English monarch King John and disrupt events in the 13th Century. Near the end of the episode, when the Doctor wins a battle of wills with the Master for control of the robot, Kamelion's appearance changes from King John to Tegan, the Doctor's female companion. The Doctor then hustles "Tegan" into the Tardis and they escape.
Tags: tv Doctor Who TG Transformation Shapeshifter