'Doctor Who': 10 Whoniverse Guest Actors Who Later Returned In Major Roles

In 'Boom', the third episode of Doctor Who's most recent season, fans were given a surprise with the appearance of actress Varada Sethu. Sethu, who was announced some months ago to be joining Ncuti Gatwa and Millie Gibson as a new companion in the upcoming season 2/series 14 of Doctor Who (reported to have recently finished filming), appeared in 'Boom' as Mundy Flynn, an Anglican Marine who becomes an initially reluctant ally to The Fifteenth Doctor and Ruby Sunday after The Doctor steps on , but does not trigger, a Villengard landmine.

However, showrunner Russel T. Davies has since revealed that Sethu, who also starred as Cinta Kaz in the Star Wars universe series Andor, will not be reprising the role of Mundy Flynn in season 2, but instead appear as an entirely new character. While this might seem somewhat unusual, it is actually quite on-brand for Doctor Who. Since the classic series, and continuing across the revival, spin-offs, and even a few of the Big Finish audio dramas, actors have appeared in guest or minor roles before returning to assume a major onscreen role within the Whoniverse.

Let's look at afew of those actors.

1. Lalla Ward

In 'The Armageddon Factor', the six-part final story of Classic Doctor Who's sixteenth season, as well as the final chapter in the series-long 'Key To Time' saga, Lalla Ward appeared as Princess Astra of Atrios. The Fourth Doctor and his companion, the Time Lady Romana (then played by Mary Tamm), work to save Astra from the Black Guardian, when it is revealed that the Princess herself is the final segment of the much sought after Key To Time.

Issues arose when Mary Tamm opted not to return the following series, after multiple stories had already been written with Romana. However, Romana's Time Lady status offered a unique salvation in the form of regeneration. Ward, who had been well received the previous series, was cast as Romana II, with the explanation that Romana had chosen her new face after taking a liking to Astra's.

Romana II, a lighter personality than her previous incarnation, remains by The Doctor's side until 'Warrior's Gate', the fifth serial of series 18, where she opts to remain in E-Space with K-9. Later novels and audio suggest he eventually made it back to Gallifrey and played a major role in the Time War. Ward continues to portray Romana II for Big Finish semi-regularly.

2. Colin Baker

'Arc of Infinity', the opening serial of Classic Who's 20th series, features Colin Baker in the role of Commander Maxil, an antagonistic Time Lord working against the Fifth Doctor and supporting the story's villains in their attempt to restore Omega. Maxil also appeared in a few novels and Big Finish audio dramas, with Baker usually reprising the role. The character was also, at one point, intended to appear in 'The Five Doctors', but a scheduling conflict prevented this.

A little over a year later, Colin Baker made his onscreen debut as The Sixth Doctor. Beneath his rainbow jacket exterior lay a slightly harsher Doctor than most viewers were used to at the time, with Baker ultimately having one of the shortest tenures of the Classic series, not even invited back to film a regeneration scene. Retrospective reviews are often much kinder to the Sixth Doctor, boosted by Colin Baker's continued enthusiasm for the role and the fandom. Baker continues to portray the Sixth Doctor for Big Finish.

3. Eve Myles

The third episode of the Doctor Who revival's first season, 'The Unquiet Dead', and the revival's first historical story, features actress Eve Myles in a guest role as Gwyneth, a servant with clairvoyant abilities in the employ of Funeral Parlor Director Gabriel Sneed. In the episode's conclusion, Gwyneth sacrifices herself to prevent the incorporeal Gelth from crossing through a rift with the aim of possessing the bodies of the human race. Gwyneth also glimpses the future, and Rose Tyler's destiny as Bad Wolf.

Showrunner Russell T. Davies enjoyed Myles' performance as Gwyneth so much that he wrote her a regular role in Doctor Who's then upcoming spin-off Torchwood. Myles plays Gwen Cooper, who becomes the newest member of Torchwood Three after being recruited by Captain Jack Harkness as a Field Agent. Initially intended to humanise the team as an audience surrogate, Gwen hardens somewhat as the series goes on, becoming willing to make ethically difficult decisions in the name of the greater good. She is ultimately the only member of Jack's original team (aside from Jack himself) to survive the entirety of the series.

Gwen makes a cameo appearance towards the end of Doctor Who's fourth series, with the Tenth Doctor and Rose assuming she must be distantly related to the Gwyneth they met in the past.

4. David Tennant

David Tennant was a fan of Doctor Who since childhood, proudly claiming The Fifth Doctor, Peter Davison, as his personal favourite. Earlier in his career, Tennant performed in a number of Big Finish's Audio Dramas set in the Doctor Who universe. One of his most notable roles was as the demon/roboman Galanar in the Dalek Empire series.

Created from human captives to become weapons for the Daleks, the Demons were designed to imprint upon the one who activates them and be endlessly loyal to them. Galanar, left behind by the Daleks, imprints upon human resistance fighter Georgi Selestru and subsequently becomes one of the biggest heroes of the story.

When Ninth Doctor Christopher Eccleston departed Doctor Who at the end of the first series, David Tennant was cast as The Tenth Doctor. Starring in the role across three species and four concluding specials, Ten became, and remains, one of the most popular incarnations of the character. In an unprecedented move in 2023, Tennant returned as an entirely new incarnation, The Fourteenth Doctor, for a trilogy of 60th anniversary specials. Fourteen then became half of the Doctor's first bi-generation, with the Fifteenth Doctor splitting from him.

Tennant continues to perform for Big Finish, most commonly as the Tenth Doctor.

5. Freema Agyeman

Prior to the filming of Doctor Who's second series, Freema Agyeman attended auditions where she read for three separate guest characters. She ultimately won the role of Torchwood One technician Adeola Ashodi in the two-part finale, 'Army of Ghosts'/'Doomsday'. Adeola is killed during the course of the story after being converted into a Cyberman.

Thankfully for Agyeman, her guest turn had come at a time when the show was on the hunt for a new companion in light of Billie Piper's impending departure, and the casting department had been impressed by Agyeman's range in the earlier auditions. She was cast as companion Martha Jones for series three, with Adeola referenced as having been Martha's cousin.

Agyeman starred as Martha for the entirety of series three, and after departing as a series regular, continued to make guest appearances through series four of Doctor Who, as well as a few on Torchwood. Sandwiched between fan favourites Rose Tyler and Donna Noble, Martha is often considered an underappreciated companion, but has gained more fans in recent years.

6. Karen Gillan

Nowadays, Karen Gillan is an MCU fan favourite for her role as Nebula in the MCU's Guardians of the Galaxy trilogy, but one of the actress's earliest roles is as a Soothsayer of the Sibylline Sisterhood in the Doctor Who episode 'The Fires of Pompeii'. Gillan appears prominently early in the episode, delivering news of The Tenth Doctor's prophesised arrival to the Sisterhood, and is later visible in a few background shots featuring the Sisterhood.

Two years after 'The Fires of Pompeii' aired, Gillan was cast as Amy Pond, companion to the newly regenerated Eleventh Doctor, played by Matt Smith. While the curvy and very Scottish Gillan was not what new showrunner Steven Moffat had in mind for Amy, who was initially conceived as a delicate, bird-like character, she won him over through a memorable audition, and instant chemistry with Smith. The Eleventh Doctor, Amy, and Amy's Husband Rory Williams went on to become one of the most popular Tardis teams in the revival's history.

Gillan speaks fondly of her time on Doctor Who, and remains close friends with Smith and Arthur Darvill, who played Rory. Both Gillan and Darvill recently attended a group holiday in celebration of Smith's 40th Birthday. Interestingly, she is not the only future Who star to have made their debut in 'The Fires of Pompeii'.

7. Peter Capaldi

In 'The Fires of Pompeii', the same episode as Karen Gillan's pre-lead appearance, Peter Capaldi guest stars as Caecilius, a sculptor living with his wife and teenage children in ancient Pompeii. After arriving in Pompeii on the day Mount Vesuvius was due to erupt, The Tenth Doctor and Donna seek out Caecilius to retrieve the Tardis after it was accidentally sold to him by a street merchant. While The Doctor is at first adamant that he cannot mess with history to save everyone, Donna convinces him to at least save someone, with The Doctor choosing to save Caecilius and his family. Capaldi also played John Frobisher, a morally dubious civil servant tasked with coordinating the Government's response to the 456 in Torchwood: Children of Earth.

Following Matt Smith's departure from Doctor Who, Capaldi, a lifelong fan of the series, was cast as The Twelfth Doctor. Often a favourite of Classic Who fans, Twelve is often more abrasive than his predecessors, and is well known for a memorable speech on the nature of War. His resemblance to Caecilius is eventually given an explanation in the series 9 episode 'The Girl Who Died', with The Doctor realising he subconciously chose his face as a reminder that The Doctor saves people.

8. David Bradley

'Dinosaurs on a Spaceship', the second episode of Doctor Who's seventh series, features David Bradley as the thief/smuggler Solomon, an unpleasant, villainous character in a similar vein to his other best known roles, as caretaker Argus Filch in the Harry Potter films, or slimy Lord Walder Frey in Game of Thrones. Shortly after playing Solomon, Bradley was cast as William Hartnell, the actor behind the First Doctor, in An Adventure in Space and Time, a docudrama chronicling the early days of Doctor Who, produced as part of the series 50th anniversary celebrations.

Bradley's performance as Hartnell, as well as in the scenes re-enacting iconic First Doctor moments, was highly praised by fans and critics alike. So, while the idea of recasting a dearly departed Classic Doctor had previously been unthinkable, Steven Moffat eventually invited Bradley to play The First Doctor in Doctor Who's 2017 Christmas Special, 'Twice Upon A Time'. Bradley starred alongside Peter Capaldi's Twelfth Doctor, as both struggled with their impending regeneration.

Bradley has now portrayed The First Doctor in a series of Big Finish audio dramas, and reprised the character onscreen a second time in the BBC centenary special 'Power of The Doctor'.

9. Bradley Walsh

While Russel T. Davies first Doctor Who spin-off, Torchwood, was aimed at older audiences, the second, The Sarah Jane Adventures, starring Elizabeth Sladen as The Doctor's former companion Sarah Jane Smith, was intended as an introduction to the Whoniverse for younger viewers. In 'The Day of the Clown', the second two part story of the spin-off's second season, actor and presenter Bradley Walsh appears as Elijah Spellman/The Pied Piper, an ancient and very creepy energy being who begins stealing the children in Sarah Jane's neighborhood.

Ten years after his appearance in The Sarah Jane Adventures, Walsh was cast as Graham O'Brien, one of the three companions of The Thirteenth Doctor. After the death of his Wife, Grace, Graham joins The Doctor to honour Grace's adventurous spirit, and watch over her grandson, Ryan. Graham departs the series as a regular at the end of series 12, but returns for a guest appearance in 'The Power of The Doctor'. It is suggested that he is the mastermind between the support group of former companions seen in the episode.

10. Sacha Dhawan

Sacha Dhawan, having performed in a number of Big Finish audio dramas, was no stranger to the Whoniverse when he was cast as Waris Hussein in An Adventure in Space and Time. Fans well versed in Who history will be aware that Hussein was Doctor Who's very first Director, as well as one of the youngest Directors ever employed by the BBC at the time, adding to the ragtag misfit feel of the show's original creative team.

Prior to Doctor Who's 2020 New Year's Special, 'Spyfall, part one' which doubled as the series twelve premiere, it was revealed that Dhawan had been cast in a guest role as O, an MI6 agent who teams up with The Thirteenth Doctor and her companions.

However, in a twist ending worthy of the Classic era, the episode's closing minutes reveal that Agent O is actually the newest incarnation of The Master, having killed the real O and assumed his identity before The Doctor's arrival. Dhawan continued to appear as The Master throughout The Thirteenth Doctor era. Now, Dhawan continues to perform his incarnation of The Master for Big Finish.