The Torchwood gang are doing their thing all over BBC One every night this week, but the eagle-eyed amongst you will have noticed that they're still a couple of members short following the deaths of Owen and Tosh last year. And with the remaining members being hunted down by shady forces, perhaps it's a good time to look at some potential Torchwood candidates from Doctor Who and The Sarah Jane Adventures, should they still need to replenish their numbers after Friday...

Mickey Smith (Noel Clarke)

When we first met Mickey Smith, he was little more than an irritant, a one-note character designed to give Rose Tyler someone to want to run away from. Many of the millions of viewers watching Rose were left thinking, 'I wish the Doctor had decapitated the real Mickey instead of the plastic one.' And yet, as the months went on, Noel Clarke managed to turn Mickey into a sympathetic character, albeit still a bit of a feckless one. But while Rose and the Doctor grew smugger, Mickey grew braver, and it was a changed man who finally ditched his peroxide bimbo in favour of a life hunting down Cybermen in a parallel universe. He's made a few reappearances since then, and last time we saw him he was following Martha and Jack as they strode off into the sunset together. Owen's death has created a vacancy in the team for someone brave but ultimately a bit dim; could Mickey the Idiot be the one to fill it?

Why it probably won't happen:
While Mickey would seem like an ideal candidate for the Torchwood treatment, what with last year's Who finale seeming to set up his presence within the team, actor Noel Clarke has bigger fish to fry. With three films in post-production and another one having just finished filming, it looks like Mickey's going to be otherwise indisposed for the time being...

Sarah Jane Smith (Elisabeth Sladen)

It's been a funny old few years for sometime-journalist Sarah Jane Smith. At the start of 2006, she was a bitter old spinster who lived in a big house with only her robot dog for company, pining after that mysterious man with two hearts she travelled with all those years ago. These days, it seems like she can't move for fear of tripping over her gang of youngsters, most notably her teenage 'son', Luke. And the wanderer from Gallifrey keeps knocking on her door for one last adventure. She still lives with the robot dog, but more on him shortly. Sarah Jane has more than proven herself still capable of fighting aliens, having saved the world from the Slitheen, the Bane and the Sontarans, to name but a few. Will she soon be taking Tosh's place as the less annoying woman in Torchwood?

Why it probably won't happen:
Journey's End showed us that Jack would probably hire Sarah in a heartbeat (even though a journalist wouldn't normally be his first choice to join the team), but it seems unlikely that she would say yes to such an offer; she's stated on numerous occasions that she disapproves of Torchwood's methods, and the move from Ealing to Cardiff would be a hell of a strain on poor old Luke. So until Jack and the gang decide to start defeating their enemies with custard pies, this is one woman who'll be keeping her distance.

Jenny (Georgia Moffett)

For some, Jenny (surname unknown) should never have happened. The by-product of arguably one of Doctor Who's weaker episodes, the Doctor's daughter was created to give David Tennant and Catherine Tate some more angsty material to perform, while Freema Agyeman wandered around fulfilling a contractual obligation with a mute alien. However, thanks to some snappy dialogue and a top-notch performance by real-life Doctor's daughter, Georgia Moffett, Jenny sprung to life as a feisty, flirtacious femme fatale who would be more than a match for whatever alien race happened to wander in her general direction. In short, Jenny would make the perfect foil for Captain Jack as they battled and bantered their way to the bedroom... What would daddy say?

Why it probably won't happen:
On paper, there's no good reason why Jenny couldn't find her way to Torchwood Cardiff. We last saw her blasting off from the planet Messaline in the far future, but experienced viewers will know that this wouldn't prove too much of a problem, particularly with Cardiff having its own space-time rift. However, the return of the Doctor's daughter feels like something that would need to be handled by the parent series. Indeed, it was incoming showrunner Steven Moffat's idea to bring her back from the dead in the first place! So until the Doctor and his daughter meet up again, this is one potential member of the gang who's firmly out of bounds. Still, there's always next year...

K-9 (John Leeson)

Having spent the last couple of years guarding a black hole in Sarah Jane Smith's attic, everybody's favourite robot dog is set to return to Earth later this year for the third season of The Sarah Jane Adventures. But with the occasionally-evil Mr Smith taking care of all the team's information needs, is there really a place for K-9 on Bannerman Road? While K-9 Mark IV hasn't had as much chance (not onscreen, anyway) to prove himself as his space-faring counterparts, he's made of the same stuff, better, even, since he was rebuilt by an older and wiser Tenth Doctor. And his cameos in Sarah Jane and Doctor Who prove that he's an excellent deus ex machina. So with Torchwood missing one computer expert, why not hire a girl's best friend to fill the void? The Hub even has (or at least, did have) a handy lift for K-9 to use, which is more than can be said for Sarah Jane's attic...

Why it probably won't happen:
As I said before, K-9 is set to return to The Sarah Jane Adventures for a six-episode stint this Autumn, so he's going to be indisposed until that's finished. After that? It's hard to say. Despite the crossover in Doctor Who, the Beeb might still be reluctant to let a child-friendly character like K-9 encroach upon the more adult Torchwood, and rightly so. K-9 would look a little ridiculous trundling around with the Torchwood gang, if we're honest. And with a K-9 series set to debut in Australia later this year, the character's fate as a children's television staple would seem to be sealed. Quite right, too. Good dog. That said, I'd give anything to see Ianto's reaction to the metal mutt.

Chrissie Jackson (Juliet Cowan)

Maria's mum, Chrissie, may seem like a strange choice to join Torchwood. She's loud, brassy and borderline rude, essentially The Sarah Jane Adventures equivalent of Jackie Tyler. But, in spite of appearances, Chrissie's a shrewd woman. She cottoned onto there being something a bit weird about Sarah Jane before her ex-husband did, even if she was a little off about the specifics. She also managed to come to the rescue of the gang when they were at the mercy of a Sontaran commander, by jamming a high heel into his probic vent. She parted company with Sarah Jane with her memory intact, and with a greater awareness of aliens and what she could do to stop them than most people. Could it be that what Torchwood really needs is an older woman to order them into line?

Why it probably won't happen:
Chrissie was intended as The Sarah Jane Adventures' comic relief, connected to a character who isn't in the show anymore. It'd also be pushing the show's boundaries to have the hormones of Chrissie and Jack raging in the same room together; they'd likely be too busy getting busy with one another to go out and fight aliens, which probably wouldn't please Ianto. There's also the question of what would happen if she happened to introduce Jack to her friend Donna Noble. Or perhaps that's just a pet theory of mine. Bizarrely, though, of all the candidates on my list, Chrissie's probably the one who'd be most likely to make the transition. Watch this space!

So that's a few of my own suggestions, but there are so many other characters I could have chosen. Who would you like to see filling the remaining places on the team? Leave your suggestions in the comments box below.