Crystal (The Ultimate Adventure)

Crystal was a nightclub singer who joined the Doctor on his travels.

Profile
Crystal worked as a singer at the Number 10 nightclub in Clarendon Square. She had played Europe but never London. At the club, she performed the song "Strange Atractor". She first met the Doctor and his companion Jason (a French aristocrat from 1789), as they tried with success to stop the Cybermen from kidnapping a US Envoy from her nightclub. She subsequently helped them stop a plot jointly originated by the Cybermen and the Dalek Emperor. Crystal and Jason soon fell in love. She sang "Sky High" with Jason, then returned to the club but she decided to join Jason and a third companion, Zog in the TARDIS. (SP: Doctor Who: The Ultimate Adventure)

Crystal, with the Doctor, Zog and Jason, later visited Leisureworld on the living planet Krennos where they uncovered a plot by the Chameleons. (ST: Face Value)

Behind the Scenes
Because of the nature of Doctor Who: The Ultimate Adventure, which starred Jon Pertwee as the Third Doctor and later Colin Baker as the Sixth Doctor (he reprised his role in the audio adaptation, as well as David Banks, filling in Jon Pertwee as the "Greenpeace Doctor" in some performances, what Doctor she "really" travelled with remains ambiguous.