Doctor Who fans all have the same idea following Billie Piper's sensational return to the series.

The English actress and former singer made her comeback on this Saturday night (May 31), nearly two decades since her departure. , 42, is renowned for her portrayal of Rose Tyler, the Doctor's companion, during the show's revival in 2005 after a 16-year break.

In the season finale, Ncuti Gatwa bid farewell to the beloved sci-fi series after 18 episodes as the titular character, with the Doctor regenerating as Piper. This followed rumours Piper might be handed the sonic screwdriver to become the Doctor herself.

However, fans are now sceptical about Piper assuming the mantle of the latest Doctor due to a particular detail. As the credits rolled, both Gatwa and the returning Jodie Whittaker were credited as The Doctor, but not Piper.

Instead, it read: "And introducing Billie Piper." This has left viewers speculating if Piper may not actually assume the role of the Doctor, or if the character might evolve differently.

A user gave their theory, stating: "So, when the new 'Doctor' appeared she looked around in surprise before saying hello. And there's no way she'd be able to know she has Rose's face that quick. Especially not without speaking or seeing herself.

"Pair that with the random shot of the TARDIS console, The Doctor seemingly fading out before Billie Piper faded in, and Billie not being credited as The Doctor, what is this is the TARDIS somehow transferring into The Doctor's body, using Rose's face as she was the last person to absorb/stare into the heart of the TARDIS. Thus the looking around and 'Oh, hello! ,' was the TARDIS being surprised it suddenly has a body."

Agreement came from another Reddit fan, who chimed in: "I think she's just Billie Piper. No mystery. Billie Piper finds herself in Doctor Who."

They then joked: "She hasn't watched for a while. She gets the Doctor Who Magazine, but just for the puzzles."

A third fan pointed out: "Well there is also the statements from both Billie and RTD that say they are excited to have her return but never actually call her the doctor. RTD's statement actually says who she is will be a mystery."

Quoting RTD, they said: "Billie once changed the whole of television, back in 2005, and now she's done it again. It's an honour and a hoot to welcome her back to the TARDIS, but quite how and why and who is a story yet to be told."

The Reddit user concluded: "I think this is pretty much confirming she isn't actually the doctor but someone else."

Piper previously told the BBC: "It's no secret how much I love this show. I've always said I would love to return to the Whoniverse, as I have some of my best memories there.

"So to be given the opportunity to step back on that TARDIS one more time was just something I couldn't refuse. But who, how, why and when - you'll just have to wait and see."