Summary

• Doctor Who season 15 introduces a new companion, played by Varada Sethu, alongside Millie Gibson's Ruby Sunday, breaking Russell T Davies' single companion rule.
• The return of Millie Gibson in Doctor Who season 15 means viewers may wait longer for answers to Ruby's many mysteries.
• Ruby Sunday and Varada Sethu's characters in season 15 must be very different in order to avoid overlapping as companions.

Doctor Who's cast beyond season 14 arose when her departure was reported in January 2024 and Varada Sethu was named as her replacement.

It now seems that Ruby Sunday will survive to see Monday, as the BBC has officially confirmed Varada Sethu will the TARDIS for Doctor Who season 15, but as an additional companion, not Gibson's replacement. Taken at face value, this announcement appears reassuring enough, assuaging concerns that Ruby Sunday's story will be cut short due to Gibson leaving. Looking deeper, however, and the revelation that Ncuti Gatwa will have two companions in Doctor Who season 15 raises new questions all of its own.

Doctor Who Season 15's TARDIS Team Breaks An RTD Companion Rule

RTD Has Typically Avoided Multiple Doctor Who Companions

For starters, Doctor Who season 15 having two full-time companions breaks an unwritten rule of Russell T Davies' Doctor Who. Previously, RTD adhered fairly rigidly to the single companion format, with Rose, then Martha, then Donna. The likes of Captain Jack Harkness would dip in and out, but RTD's original era of Doctor Who only ever had one full-time companion in the TARDIS at any given moment. The new message from the BBC very strongly positions Gatwa, Gibson, and Sethu as a leading trio of main characters, and that represents a big deviation from RTD's usual Doctor Who setup.

RTD spearheaded the concept of Doctor Who companions as important, central characters, and one of the ways he achieved that was by ignoring the notion of a TARDIS "team."

Expecting RTD to do everything exactly as he did in 2005 is pointless (although perhaps not, judging by the number of returning faces on and offscreen) but the lone companion format did serve a distinct purpose. Doctor Who companions of the classic era were written infamously thinly. Far from the fully-formed companions Doctor Who peddles today, their predecessors could count themselves lucky if they had two dimensions. Starting with Billie Piper's Rose, RTD spearheaded the concept of Doctor Who companions as important, central characters, and one of the ways he achieved that was by ignoring the notion of a TARDIS "team."

Whether it was Rose and the Tenth Doctor's love story, Martha and the Tenth Doctor's non-love story, or Donna and the Tenth Doctor's wonderful "partners in crime" friendship, focusing on one Doctor/companion dynamic at a time served RTD's Doctor Who era well. Abandoning that for Ruby Sunday and Varada Sethu's as-yet-unnamed character in season 15 would, at the very least, involve great risk.

Ruby Sunday's Role In Doctor Who Season 14 Now Looks More Confusing

How Will Doctor Who Season 14 Handle Ruby's Story Now?

At face value, it would appear that reports of Millie Gibson's Doctor Who exit were simply inaccurate. Again, however, there is more to consider here. The news was first reported by the UK's Daily Mirror newspaper, then later confirmed by Variety. The report also - accurately, as it turns out - named Varada Sethu as Doctor Who season 15's new companion.

After Gibson's Doctor Who departure was reported, Ncuti Gatwa himself posted a message of on his social media. Gatwa did not acknowledge the rumors explicitly, but certainly seemed to be responding in a tacit way. Additionally, on-location photos emerged in January 2024 showing Varada Sethu shooting scenes alongside Gatwa for Doctor Who season 14, and Millie Gibson was not present.

Doctor Who season 14 is being marketed as "season 1" (and season 15 as "season 2")

All of this could have a simple explanation. Gatwa's social media post may have been a straightforward show of love as Gibson became the subject of rumors, and the leaked set photos may be taken from a scene Ruby Sunday wasn't scripted to appear in. Whatever the case, Doctor Who's dual-companion announcement confirms a resolution has now been found, although whether the plan was always for the Fifteenth Doctor to have an additional companion alongside Ruby Sunday in season 15 remains unclear.

UPDATE: Russell T Davies has now confirmed reports of Millie Gibson's Doctor Who exit were only rumors.

Gibson's confirmed return in Doctor Who season 15 means some of those mysteries may now rumble on and viewers will wait longer for answers.

The more important question is what this narrative of uncertainty means for Ruby Sunday's story in Doctor Who season 14. Previously, it appeared that the episode "The Legend of Ruby Sunday" would resolve most of the mysteries surrounding Millie Gibson's character - her parentage, her neighbor, the cloaked woman, etc. - then Ruby would be written out of the show, closing that chapter of the Fifteenth Doctor's journey for good. Gibson's confirmed return in Doctor Who season 15 means some of those mysteries may now rumble on and viewers will wait longer for answers.

It will also be interesting to see whether Doctor Who season 14 ends with the Doctor and Ruby riding off in the TARDIS towards their next adventure, or whether Ruby's fate will be left somewhat ambiguous. The original Daily Mirror report revealing Gibson's exit stipulated that the actress would not appear in 2024's Christmas special, but would make a "handful of appearances across Ncuti’s second series as the Doctor during 2025." The BBC's position strongly states that Gibson and Sethu will both be companions in Doctor Who season 15. "The Legend of Ruby Sunday" may contain a secret twist that makes Ruby's future role clearer.

Doctor Who's New Companion Pairing Must Avoid The Most Obvious Misstep

Can Doctor Who's Two Companions Coexist?

The TARDIS pairing of Millie Gibson and Varada Sethu in Doctor Who season 15 is an unusual one - both in comparison to the modern series and the classic years. The Doctor is, at this point, renowned for recruiting young women and girls from Earth as companions, despite having all of time and space to choose from. What is rare, however, is for the Doctor to have two at a time.

Ruby Sunday is an archetypal modern Doctor Who companion - young, strong-willed, slightly mysterious, intelligent and curious, female, carrying unrealized potential, and from Earth. Ruby's character is cut from the same cloth as Rose, Martha, Amy, Clara, Bill, and Yaz. The challenge for season 15 will be making Varada Sethu's Doctor Who character completely different from Ruby Sunday. If her character also adheres to the same standard modern companion mold, the TARDIS may not be big enough for both of them.

This is not an obstacle Doctor Who has needed to overcome before, usually relying on broader factors such as age and backstory to differentiate between companions. Dan being an older, more experienced figure compared to Yaz immediately set him apart, ensuring Thirteen's final two companions had very different voices and roles in the TARDIS. The same was true of Bradley Walsh's Graham, while Nardole not hailing from present-day Earth made him totally unlike Bill, and Ian and Barbara being Susan's schoolteachers made them distinct from the Doctor's granddaughter.

The closest equivalent would be Tegan and Nyssa from the Fifth Doctor's time. This pair, however, were separated as characters by Nyssa's unique alien origin, as she hailed from Traken. Additionally, Nyssa's intelligence was closer to the Doctor's, making her an entirely different companion than Tegan, and allowing them to each occupy their own individual spaces in the narrative. Doctor Who season 15 could repeat this strategy to solve its own companion dilemma, giving either Ruby or Varada Sethu's character an extra-terrestrial backstory in order to clearly define their respective roles in the show.

Doctor Who season 14 premieres May 10 on Disney+ and May 11 on iPlayer.