<P> The Master showed a dramatic personality change upon regenerating into the Mistress / Missy . In that form, she wants nothing more than to renew her bond with the Doctor, even calling him her "boyfriend" at one point . ("Deep Breath, Death in Heaven") When she met him again, Missy pretended to be an android and kissed him passionately . ("Dark Water") Despite still being manic and a psychopath, she later showed a willingness to reform, spending centuries in the Doctor's custody as a show of her commitment . Later, she felt torn between the Doctor, who represented her repentance, and her past incarnation, who represented a return to her old ways; she ultimately chose the Doctor, for which her past incarnation killed her in disgust ("The Doctor Falls"). </P> <P> The Doctor has always regenerated into a humanoid form . However, when explaining the process of regeneration to Rose at the end of "The Parting of the Ways", the Ninth Doctor suggests that his new form could have "two heads", or even "no head", and in the 2005 Children in Need special, which takes place immediately after that episode, the newly regenerated Tenth Doctor, while examining his new body, makes a point of checking that he has two arms, two legs and two hands, implying that regenerations can sometimes result in physically deformed or non-humanoid forms; it is not clear whether or not these two moments are intended as jokes . </P> <P> Whether Time Lords could change gender in regeneration was never addressed onscreen during the classic series and not explicitly focused on for much of the revival . In the second part of The End of Time (2010), the Eleventh Doctor briefly checks for an Adam's apple upon regeneration to confirm if he is still a man . In "The Doctor's Wife" (2011), he reminisces about an old friend and fellow Time Lord, the Corsair, who had been both a man and a woman several times . In "The Night of the Doctor" (2013), the Sisterhood of Karn specify the Doctor could choose to change sex using one of their elixirs which influence the outcome of regeneration . "Dark Water / Death in Heaven" (2014) shows that the Doctor's longtime nemesis the Master has become a woman, taking the name Missy . In "Hell Bent" (2015), the Time Lord General regenerates into a younger woman, and states that her previous incarnation was her only male form . In "World Enough and Time" (2017), the Doctor tells his companion Bill Potts, in reference to Missy, that Time Lords are mostly beyond gender norms and stereotypes; however, Bill points out that the males and females of the species collectively refer to themselves by a male title . From "Twice Upon a Time" onward, Jodie Whittaker will portray the Thirteenth Doctor, the Doctor's first female incarnation . </P> <P> Female Doctors were previously explored in spin - off productions; Joanna Lumley played the Thirteenth Doctor in the 1999 Comic Relief spoof The Curse of Fatal Death, and Arabella Weir played the Doctor in the 2003 Big Finish audio drama Exile . Spin - off media have also depicted more drastic regenerations than the TV series . For example, in the Big Finish Productions audio Circular Time, a Time Lord known as Cardinal Zero regenerates into an avian life - form after being poisoned . </P>

When was it established that time lords can change gender