Throughout its more than half-century on air, Doctor Who has presented us with many memorable supporting characters. Some have been lucky enough to get their own series' either on television (as was the case with Torchwood and The Sarah Jane Adventures) or on audio via Big Finish (Jago & Litefoot and the Counter Measures team from 1988's Remembrance Of The Daleks). While the RTD era gave us the aforementioned TV spin-offs, the Moffat era has to date not quite managed that feat, although a particular triofeatured in their own number of mini-episodes online as well as their own novella. But what if that particular trio of Madame Vastra, Jenny Flint, and Strax (or, as their better known, the Paternoster Gang) had their own spin-off series?Before we look at that question, perhaps we should look at another question: what is it about the Paternoster Gang that makes them popular with fans? On the surface, they're the most unlikely mix of characters. There's the Silurian Madame Vastra (played by Neve McIntosh), the Victorian era British female Jenny Flint (played by Catrin Stewart) and, perhaps the most unlikely of all of them, the Sontaran Strax played by Dan Starkey. All three were introduced in Series Six mid-season finale episode A Good Man Goes To War though both McIntosh and Starkey had played other members of their characters respective alien races previously (McIntosh played Siluran sisters in the previous season's Hungry Earth/Cold Blood and Starkey Commander Skorr in The Sontaran Stratagem/The Poison Sky back in 2008).Brought together from across space and time, the trio were amongst those gathered for the Battle Of Demon's Run. Almost instantly, the group seemed to gel together with the Victorian duo of Vastra and Jenny armed with swords and doing battle while Strax, despite being a Sontaran, managed to be memorably scene stealing with some great comedic moments. Despite Strax's apparent death at the end of the episode, it wasn't long before the trio returned in the following year's Christmas special, The Snowmen, and its online prequels. This return appearance only seemed to confirm the trio's chemistry both with one another, with Vastra and Jenny being the implied inspirations for Sherlock Holmes and Doctor Watson and Strax's continued comedic moments, and their chemistry with Matt Smith's Doctor in particular. The trio returned twice more alongside Smith's Doctor in The Crimson Horror where they effectively became the leads for the episode's first half, as well the finale episode The Name Of The Doctor, before returning to help launch Peter Capaldi's Doctor in 2014's Deep Breath. They've become arguably the most recognizable supporting characters of the Moffat era with their unlikely combination of detective, action and comedy so it's perhaps no surprise that there's been some call for a spin-off featuring them.But what would such a series entail? Perhaps the best idea we can get from their appearances is 2013's The Crimson Horror. The episode is a combination of Sherlock Holmes, The Avengers (that would be the one with Steed and Mrs. Peel) and of course Doctor Who itself. The Holmes influences are particularly strong in the opening minutes with Vastra engaged on the case, as well as her investigations throughout the episode. The Avengers influence can be seen in Jenny, from her attempts to influence the Sweetville community (which, with is mysterious factory, also has echoes of Nigel Kneale's seminal Quatermass II from 1955) which goes right down to the catsuit like outfit she wears during the episode's latter half. The science fiction nature of the plot owes much to Doctor Who, of course, but the combination of all these elements made for one of the most memorable and enjoyable offerings of series seven. It also gives us some idea as to what “formula” (for lack of a better word) a spin-off series might use, as well as to what roles the characters could play within it.There's more that could be done with them of course. The insinuation made in The Snowmen that the gang (Vastra and Jenny in particular) were the inspiration for Conan Doyle's Sherlock Holmes and Doctor Watson offers another possible avenue for exploration in a series where viewers might be presented with the “real” inspirations for the Holmes stories. One that brings to mind is The Hound Of The Baskervilles which, with its titular beast, has become the most filmed of all Holmes stories. Its atmosphere and subject matter would seem to perfectly suit a series featuring the gang. The Avengers influence also presents opportunities with that show's well established formula being transported back to the Victorian era. Ties back to Doctor Who itself could be called for as well, something that could perhaps fill in the off-screen events mentioned in episodes such as A Good Man Goes To War - including Vastra's awakening in Victorian London and her encounter with Jack The Ripper prior to her on-screen introduction (the former being something which might also give the opportunity for Matt Smith to reprise the role of the Doctor, a piece of publicity that could help to give a new series a boost both in ratings and media attention).Outside of what such a series might entail, the other obvious question is how viable is it? As RTD himself noted back in 2009 in the BBC Radio 2 program Who On Who, with the budgets cuts the BBC has been facing shows like Torchwood and The Sarah Jane Adventures were unlikely to be commissioned in the Moffat era. Indeed the Moffat era, as stated a few paragraphs above, has yet to produce a spin-off series of its own. Perhaps that's because Moffat (alongside Crimson Horror writer Mark Gatiss) has been busy on the BBC's hit series Sherlock. There's also the fact that period settings are expensive to do, and even if a period based series is successful with viewers it can still be easily canceled on the justifications of cost, as has happened with shows including the 1950s set drama The Hour, ITV 1940s set Foyle's War and the BBC's own Victorian crime drama Ripper Street. Add on the costs of make-up every episode for Vastra and Strax alone without the addition of anything else and a possible TV series might seem like an expensive and risky venture.Which is where another recently announced New Who related spin-off comes in. In a move that surprised many, Big Finish Productions have announced the revival of their UNIT spin-off series , but this time featuring the character of Kate Stewart in the lead. It's the first time that the company has been able to produce stories featuring any characters from the New Series (meaning anything that's been on the TV series since 2005) and a very obvious tie-in to the show's current era. It also creates a precedent that's worth exploring here as well.Given that the visuals are the most expensive elements of a possible Paternoster Gang, perhaps audio is the way to go. As listeners to Big Finish's prodigious and award winning output will know, the format more than makes up for its lack of visuals with its ability to focus on characters and performances alongside sound design and music to create the auditory equivalent of a TV show or movie on a fraction of the budget. Plus Big Finish has already proven, via the successful Jago & Litefoot box-sets, that a Victorian based Who spin-off is entirely workable even across multiple box-sets. In fact, Big Finish would be the only practical way of bringing that duo from Talons Of Weng-Chiang with the Paternoster Gang in what could be an interesting crossover of characters from both old and new Who. Is a series of audios (or more likely audio box-sets) something that could it be made to work as a viable product? Perhaps the success of the upcoming UNIT box-set might help answer that question.In the final analysis then it would appear that there's potential here to be sure. The combination of the Paternoster Gang characters, their chemistry with one another, the Victorian setting and the indications of what we've seen on-screen so far all point to some intriguing possibilities. The real questions about giving them their own series then are the same ones facing any new television series: how viable is it financially and how successful would it be with viewers? That, as the Bard once wrote, is the question...