The season finale of Doctor Who, ‘The Reality War,’ was shocking for many reasons. However, the biggest surprise involved an appearance by actress Billie Piper, who played Ninth and Tenth Doctor companion Rose Tyler.

Doctor Who star Ncuti Gatwa has quit the show and passed his Time Lord baton to Billie Piper — but fans believe all is not what it seems. This weekend's season finale saw Gatwa leave the BBC's big sci-fi show after 18 episodes in the title role,

Ncuti Gatwa regenerated into Billie Piper in the series finale of Doctor Who on Saturday night. He left the role after playing the iconic character for two series. Piper, who previously played the Doctor's assistant, Rose Tyler, said the opportunity to "step back on that Tardis one more time was just something I couldn't refuse".