Crystal (The Ultimate Adventure)

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

Biography
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 as a stage play which featured at various times the Third Doctor, the Sixth Doctor, and a unique stage-only Doctor, which Doctor Crystal "really" travelled with remains unclear.
 * The audio adaptation of this story and the sequel short story feature Crystal travelling with the Sixth Doctor, clearing up the question so far as BFA and PDA continuity are concerned.