Undercover.
All familiar characters belong to BBC.
Gwen
Gwen would rather just ask, nicely. Sneaking isn't really a strong suit of hers. When she goes undercover she becomes perky and obvious. And as a rather perky person usually, an overly perky Gwen is very clearly trying to hide something. Even complete strangers easily pick up on it. She's much better at just annoying someone into giving her what she wants by being overly persistent. Appealing to their humanity. Guilting them. Or when all else fails, just entering cop mode and just demanding it.
She's also, according to Owen, "positively shit at accents."
Her stock retort is who needs accents when a Welsh woman in Wales is what people expect anyways.
Tosh
Tosh would rather just stick to her tech projects. She's not a people person like Gwen and never will be. She trips over herself; she's not good at improvising excuses for her presence quickly.
What Tosh is great at is supporting others who are going undercover, from behind the scenes. She works with alien technology to introduce the others to the contact lenses. She can hack her way into a government database and create a fake person from birth certificate to minor traffic infraction. She'll guide them through schematics and blue prints like it's mission Impossible. And it is basically Mission Impossible with this lot sometimes.
Owen
No one lets Owen go fully undercover after the Weevil Fight Club incident. Truthfully he thinks the bunch of tossers are just prejudice against him for being dead. He refuses to concede the point not being able to eat food actually makes him more liable to blow his cover.
Ianto
Ianto is actually really quite good at this, he'll have you know. He's perfected the art of staying in the background, being just present enough that people remember there's a butler to grab the coffee from, and a quick enough server no one pointedly wonders what happened to him. No one ever asks him personal questions, tries to get to know him as anything other than the well-dressed teaboy. He's perfectly invisible. Or he would be. If it weren't for the fact trouble tends to find him quickly and spectacularly. He is a right magnet for it. But at least he's not Jack.
Jack
Jack is actually well trained in undercover work. He was a time agent, after all. And like a good time agent, he was taught how to find clothing to fit in. Which organizations to align himself with. What to jot down on the 'ole physic paper when he needs a good cover story.
And he threw all of it away because seriously, why bother.
Being flash, loud and brash gets you what you want. Hiding in the shadows doesn't exactly suit a face like his. He refuses to let the coat go, he introduces himself by rank, first and last name, in that order. Taking a fake name loses its point when you wear it proudly as your own, but again, Jack can care less. Because why bother sneaking when you can just let the world know you're there? And you have authority over them.
What are they going to do? Kill him?
Besides, Retcon is the new "not blowing your cover".
Rhys
Rhys doesn't even technically work for this lot, but goes undercover for them anyways because they seriously need some help.