Sarah Jane Smith (Elisabeth Sladen)
Resourceful Metropolitan journalist Sarah Jane Smith met the Doctor while posing as her virologist aunt, in an attempt to infiltrate UNIT's security. Stowing away in the TARDIS, she quickly found herself in mediaeval England.
Sarah's curiosity, and her feminist views, frequently got her into trouble, but she relished her adventures with the Doctor. She witnessed the Doctor's regeneration into his fourth incarnation, and continued to travel with him until a call from the Time Lord's home planet forced him to return her to Earth.
Later the Doctor sent her a present: a robot dog named K9.