Welcome back to Doctor Who, Billie Piper! The British sci-fi series just shocked fans when, in the Season 2 finale, Ncuti Gatwa ‘s Doctor regenerated — and the Sixteenth Doctor appears to be played by none other than Piper!

And, of course, the 14th Doctor was played by David Tennant who ended up reuniting with Donna Noble (Catherine Tate) where he continues to live now after Ncuti’s version bi-generated out of him (which could come to play in a later theory…)

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".