David Tennant’s return as the 14th Doctor in Doctor Who was widely publicized before it happened, and while it changed the series’ established norms, Russell T. Davies had an even greater surprise in store for fans during the season finale of Ncuti Gatwa’s second season as the 15th Doctor – an unexpected regeneration.

As if that twist wasn’t enough, the new face that Gatwa’s Doctor morphed into is just as well-known to Who enthusiasts as David Tennant’s – that of former companion Billie Piper. Piper portrayed Rose Tyler during the show’s revival with Christopher Eccleston and remained with the series through much of David Tennant’s original tenure. Now, it appears she is the Doctor, leaving fans bewildered.

Doctor Who season 2 star cast

The season finale, titled The Reality War, featured the Doctor, Belinda Chandra (Varada Sethu), and Ruby Sunday (Millie Gibson) confronting the “Unholy Trinity” comprised of the Ranis (Archie Panjabi and Anita Dobson), Conrad Clark (Jonah Hauer-King), and Omega – as they fought for the very fabric of reality.

In typical emotional fashion, The Doctor paused at the end of the episode to check on his latest companions, but in an unexpected moment that caught everyone off guard, he regenerated, allowing fans a brief glimpse of Piper in her new form.

As of now, there has been no indication regarding the series’ future, with Davies being cryptic about upcoming developments. He previously mentioned:

“There are no decisions until after season 2. It’s amusing because even those who work on the show believe that means we’re holding secret discussions about it. People I collaborate with each year ask, ‘What’s happening?’ and I respond, ‘Nothing! No meetings, nothing.'”