Doctor Who’s Surprise “Boom” Guest Star Calls Back to an Eleventh Doctor Era Twist

This Doctor Who article contains spoilers.

Back in 2012, Doctor Who fans freaked out. We’d been told in advance that Clara (Jenna Coleman) would eventually replace Amy (Karen Gillan) and Rory (Arthur Darvill) as the next companion of the Eleventh Doctor (Matt Smith) in series 7 of the show. But fans weren’t prepared for just how soon Coleman would make her Doctor Who debut. Although she wouldn’t officially join Matt Smith in the TARDIS until a few episodes later, Coleman first appeared in the series 7 premiere “Asylum of the Daleks” as a seemingly different character named Oswin, who, although she met a tragic end, encouraged the Doctor to remember her.

And now, 12 years later, it looks like Who history is repeating itself. In the absolutely wonderful Steven Moffat-penned episode, “Boom,” the Fifteenth Doctor (Ncuti Gatwa) encounters a host of new allies, including a marine named Mundy. For fans of Star Wars: Andor, the actress playing Mundy will be instantly recognizable. That’s Varada Sethu! Yes, she was Cinta in Andor, but, as Who showrunner Russell T Davies and various news reports recently confirmed, Sethu is also joining Team TARDIS as a new companion in series 15 of Doctor Who, alongside Ncuti Gatwa’s Doctor and Millie Gibson’s Ruby. So, like Coleman back in 2012, Sethu is crashing the Doctor Who party earlier than we expected. What does it mean?

Mundy and the Anglican Marines

First, a little bit about Sethu’s character Mundy. Without spoiling too much of the plot of “Boom,” Mundy is a member of the “Anglican Marines,” religiously ordained soldiers who previously appeared in the Eleventh Doctor episodes “Time of the Angels,” “Flesh and Stone,” and “A Good Man Goes to War.” In other words, they’ve popped up a few times in Moffat’s past Who episodes, but why did he choose to introduce Mundy as a gun-toting cleric in “Boom”?

Moffat explained to Screen Rant: “[The Doctor] has slightly borderline irrational anger at soldiers and religious people, even though he’s full of faith and is pretty much a warrior himself, all self-loathing. I think it just gets him a bit wound up, and I wanted to wind him up. A soldier with a clerical collar, who he ends up really liking, of course, is the perfect person to face him with when he is trying to control his mood state on a smart landmine.”

But the last time we saw the Anglican Marines in “A Good Man Goes to War,” they were going up against the Doctor in his fight to save Amy. So, is Mundy technically aligned with the bad guys?

“I never saw them as straightforward bad guys, to be honest, at all,” Moffat revealed to Screen Rant. “In ‘Time of Angels’ and ‘Flesh and Stone,’ Father Octavian is the most heroic character there. The way he dies to save the Doctor, and the Doctor realizes throughout that story that he’s misjudged him brutally, as he’s inclined to, just because he gets wound up. He’s a scientist adventurer who has a slight suspicion that he might be God himself, so he just gets really annoyed at that.”

Varada Sethu Won’t Be the First Actor to Play Multiple Roles on Doctor Who

When it comes to Sethu’s Mundy, the relevant detail is that she survives her debut episode. This is in stark contrast with Coleman’s first appearance in Doctor Who, as well as the time Freema Agyeman popped up in Doctor Who’s “Doomsday” a full season before she appeared as Martha Jones in “Smith and Jones.” Agyeman’s first Who character was Adeola, though we were later told that was Martha’s cousin and that they just happened to look identical. 

In fact, there’s a very long history of Doctor Who accidentally casting actors in small roles, and, later, bringing them back in bigger roles. Lalla Ward appeared as a character named Princess Astra in the January-February 1979 Doctor Who serial “The Armageddon Factor.” By September 1979, Ward became the second known regeneration of the Time Lord Romana, starting with “Destiny of the Daleks.” Hilariously, in her first appearance as Princess Astra, Ward starred alongside Mary Tamm, who played the first Romana. “Destiny of the Daleks” finds Romana II telling the Fourth Doctor (Tom Baker) that she chose to look like Princess Astra on purpose, lamp shading the return of Lalla Ward in a different part.

Doctor Who later did this exact same thing when Peter Capaldi played the Twelfth Doctor, after having previously played Lobus Caecilius in the Tenth Doctor (David Tennant) episode “The Fires of Pompeii.” In the 2015 episode “The Girl Who Died” the Twelfth Doctor remembered when he was David Tennant, and rescuing a guy who looks like Peter Capaldi!

How Will Varada Sethu Return in Doctor Who Series 15?

Now, it’s unclear which kind of early cameo we’re dealing with relative to Sethu’s surprise debut. Did Davies love Sethu so much in “Boom” that he decided to offer her a bigger role in series 15? Or was this introduction always part of the plan for Sethu? Either way, what’s unclear now is how she will fit into the larger canon once she returns next year. What we know for sure is that when Sethu returns, it won’t be as Mundy, as revealed by Davies after the UK broadcast of the episode.

“It’s a delight to welcome Varada to Doctor Who, earlier than expected, though things are about to get timey-wimey,” Davies said in a statement on Twitter. “That’s the end of Mundy Flynn’s story, so quite how Varada returns will be revealed next year.”

The timey-wimey history of Doctor Who makes it quite easy to imagine Sethu coming back as a completely different character in series 15—or as a different version of Munday, just as Coleman’s Clara did across series 7. As various versions of Clara (and Oswin), Coleman became known as “The Impossible Girl.” After her apparent death as Oswin in “The Asylum of the Daleks,” Coleman appeared again in “The Snowmen” as a barmaid/governess living in Victorian England, only to die again. This created a strange kind of magical mystery, which, eventually resulted in present-day Clara becoming the one person who saved various versions of the Doctor throughout the character’s history.

When asked about by THR about the similarities between Sethu’s debut and Coleman’s, Moffat simply offered, “Yeah. Well, no, we’re just doing it again. I mean, I was talking to Russell about what we’re going to do, but she’s there! We’re just going to do Clara again. So it’s fun, isn’t it? It wakes you up. You think, “Ah, there she is!” But when the outlet inquired whether Sethu was cast for series 14 knowing that she’d be back as a companion in series 15, Moffat gave up nothing, saying only that “there is a plan. That’s all I’m telling.”

Whether we’re looking at another Clara situation or not, Sethu’s Mundy doesn’t seem impossible or magical in “Boom.” She’s a down-to-earth character who is clearly changed by encountering the Doctor. What happens when Sethu rejoins the TARDIS next year though, is, for now, anyone’s guess. As is always the case on this long-running show, time will tell—and it wouldn’t be true Doctor Who if everything happened in the right order. What would be the fun in that?

Doctor Who airs on the BBC in the UK and streams on Disney+ in the US.