Perpugilliam Brown, better known as Peri, accompanied both the Fifth and Sixth Doctors.  She was played by Nicola Bryant and was an American college student (her passport lists her residence as Pasadena, California) majoring in Botany. Peri was with the Doctor from 1984 to 1986, appearing in a total of 11 stories (collectively made up of 33 episodes).  Nicola was absolutely lovely to meet and is a really keen supporter of animal charities.  She loved her little character.