Bill Potts is a companion of the Twelfth Doctor. Bill works at St. Luke’s University during the time the Doctor is teaching there. Bill starts sneaking into The Doctor's lectures and he soon takes notice of her. Upon seeing the potential in Bill, the Doctor starts privately tutoring her. When Bill and the Doctor deal with Bill’s her new crush, Heather, being transformed into a time-travelling sentient oil being, Bill discovers that the Doctor really is an alien, and at the Doctor’s invitation, joins him on the TARDIS. In one of their travels, Bill is injured and converted into a Cyberman against her will. She is later rescued by Heather, who transforms Bill into an sentient oil being like herself.