Millie Gibson as Ruby Sunday in Doctor Who
(BBC)

What’s Going on With Ruby Sunday in ‘Doctor Who’?

Something is going on with the Doctor’s (Ncuti Gatwa) newest companion, Ruby Sunday (Millie Gibson), in Doctor Who, and fans have a few interesting theories about the mysterious character.

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Ruby made her debut in the 2023 Christmas special, “The Church on Ruby Road.” It is revealed she was abandoned at a church on Christmas Eve as an infant. As an adult, she has searched for her biological mother but hasn’t had any success. It is an interesting backstory for a companion, especially since The Doctor’s time travel capabilities would make her eager to return to the night she was abandoned. However, following the premiere of series 14 (otherwise known as season 1), it’s quite clear there’s more to Ruby’s story.

In “Space Babies,” The Doctor is left dumbfounded when his memory of the night of Ruby’s birth suddenly changes so that the mysterious cloaked mother turns and points at him before leaving. Additionally, in all three series 14 episodes so far, she has randomly caused it to snow, just like the snow that fell on the night she was born. The Doctor declares he has never seen anything like it. In “The Devil’s Chord,” the enormously powerful Maestro (Jinx Monsoon) is scared of Ruby and the song within her. Finally, in “Boom,” when Ruby is scanned by a virtual “ambulance,” it places her age at over 3,000 years old. Needless to say, viewers are starting to wonder what exactly is going on with Ruby.

The top Ruby Sunday theories

Millie Gibson as Ruby Sunday and Ncuti Gatwa as the Fifteenth Doctor in the 2023 Doctor Who Christmas Special
(BBC)

Several fan theories have arisen about Ruby’s true identity in Doctor Who. Most are fairly certain that the key to the mystery lies in the identity of her birth mother. Meanwhile, some believe she is also tied to a secondary mystery in the show: Susan Twist. Viewers recently noticed that the actress has had small roles in every episode this season, as well as in the Christmas special and one of Doctor Who‘s 2023 anniversary specials. Although the show occasionally casts the same actors/actresses in different roles, it never does so across consecutive episodes in the same season.

As such, even though Twist’s role shifts each episode from a maid to a space station commander to a concertgoer, viewers suspect they are all the same person, which means she is popping up across a span of nearly 20,000 years. This could mean that she’s a Time Lord or part of “The Pantheon” of god-like beings, which includes The Toymaker (Neil Patrick Harris) and Maestro. Some suspect she is the one Maestro referred to as The One Who Waits. Meanwhile, others suspect that Twist is Ruby’s mysterious mother. If Twist is not human, it would explain the odd occurrences around Ruby and why The Doctor’s memory changed.

However, another theory is that Twist is Ruby, perhaps an alternate-reality version of her. Then, there’s a theory that Twist is Susan Foreman, The Doctor’s granddaughter who hasn’t been seen in the series since the show’s classic era. Viewers noticed that The Doctor name-dropped Susan in “The Devil’s Chord” and mentioned his fatherhood in “Boom.” It’s possible these mentions aren’t random but tease Susan’s long-awaited re-entry into the series. Meanwhile, there’s another interesting theory that Susan is also Ruby’s mother or grandmother, as well as “The One Who Waits,” as she has been waiting for The Doctor for decades. Yet another possibility is that Ruby is a regeneration of Susan.

Some Redditors have suggested Ruby is part of the Pantheon with The Toymaker and Maestro. Since The Toymaker embodies the concept of games and Maestro the concept of music, perhaps Ruby embodies a concept, too. Users have suggested she may embody companionship, memory, or coincidence. Additional theories posit that Ruby could be the daughter of The Doctor, Missy/Master (Michelle Gomez), or River Song (Alex Kingston).

Although there are numerous theories surrounding Ruby, the general consensus is that she is not fully human and is either related to The Doctor, the Time Lords, or the Pantheon. So far, the strongest theory is that she is the daughter or granddaughter of Susan, as it would explain the multiple mentions of The Doctor’s family, why Ruby’s mother points at The Doctor, and Ruby’s strange abilities. It would also finally resolve Susan’s mystery as, for decades, the show has failed to confirm whether she is dead or living. Still, the theory doesn’t answer every mystery, such as why she boasts abilities that surprise even The Doctor and how she has partaken in DNA tests and been scanned by The Doctor with no one identifying she isn’t fully human.

Ultimately, only time will tell what’s really happening to Ruby Sunday in Doctor Who.

New episodes of Doctor Who drop Fridays on Disney+ worldwide and Saturdays on BBC iPlayer in the U.K.


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Rachel Ulatowski
Rachel Ulatowski is a Staff Writer for The Mary Sue, who frequently covers DC, Marvel, Star Wars, literature, and celebrity news. She has over three years of experience in the digital media and entertainment industry, and her works can also be found on Screen Rant, JustWatch, and Tell-Tale TV. She enjoys running, reading, snarking on YouTube personalities, and working on her future novel when she's not writing professionally. You can find more of her writing on Twitter at @RachelUlatowski.