It's a baking afternoon in June, blue skies, no traffic. The Guardian has come to a deserted university campus on the outskirts of south London to watch the second series of Misfits being filmed. But apart from the odd orange jumpsuit hanging up, there's not much to indicate that the building has found a new life doubling as the community centre where the asbo superheroes spend their days swearing, smoking and accidentally killing probation officers, until Robert Sheehan's unmistakable Irish accent breaks the summer silence at full volume: "MONKEY SLUT IS BLOWN! MONKEY SLUT IS BLOWN!"

The actor's back on set for the second series, shooting what turns out to be the centrepiece of this Thursday's opening episode. As Nathan, the gobby kid who'll never use one word when seven will do, his job today involves pounding the life out of a mouse with a baseball bat (to be fair, he thinks it's a shape-shifting villain), then strangling co-star Iwan Rheon (Simon) while they slam each other up against a bunch of lockers in a messy scrap that culminates with Nathan being impaled on a large pipe. On screen, this punch-up is over in minutes – here it takes all day. When we grab a moment with them both between takes, they're still in makeup. Iwan chats away, oblivious to the blood plastered down the side of his face as he talks about the influence of Ian Curtis on his character ("a brilliant person to sort of base Simon on"). Meanwhile, the realistic-looking pipe sticking out of Robert's stomach somehow adds to his natural charm. It's disconcerting and funny, all at the same time – just like Misfits.

E4's drama was one of the surprise hits of 2009. When it went up against BBC's Spooks, The Street and Being Human for Best Drama Series at this year's Baftas, no one really expected the show about a bunch of superpowered asbo kids to be the one walking home with the honours – least of all the Misfits themselves, who still sound like they're in shock. "We showed up with the default setting that we weren't going to win, and were just happy to be there and have a nice suit on," says Robert. "We all thought The Street would get it," adds Iwan.

Misfits sounded like it was going to be another example of commissioning maths – high on concept, low on content – where a hot topic is lifted from the headlines (asbo kids), pushed into the blender with some genre television (Heroes) and then sexed up with the stylings of another recent success (Skins).

There are elements of that "Skins meets Heroes" shorthand in its mix, but what makes Misfits work is the way it takes the framework and then hurtles away from it in leaps and bounds. By saying it's a superhero show, writer Howard Overman established the rules quickly – it's a world where stuff like invisibility or turning back time is possible – but each episode is much more interested in playing with the characters than their powers. Like the X-Men they've got team outfits, but they're scrappy community service jumpsuits, not Kevlar and capes. You don't get heartfelt speeches about the great responsibility that comes with great powers, you get an understated (and very British) reaction: it's a total pain. "They're not superpowers that make them superheroes so they can fight crime and stuff, they're actually just really rubbish, more of a hindrance than anything," Iwan laughs. "Mine's just a curse!" agrees Antonia Thomas, who plays Alisha, an already feisty character whose ability is to fill people with lust whenever they have any contact with her skin. "You really can't touch anyone or anything without them going a bit mental. I definitely drew the short straw!"

'It has completely changed my life; I have to pinch myself, thinking, "God, am I really Kelly out of Misfits? I'm in Misfits!" – Lauren Socha

Photograph: Mark Johnson

The powers aren't just the result of a mysterious lightning storm, they're more like an outward manifestation of their inner insecurities. Curtis, the athlete who's messed up a promising career, gets to turn back time ("but he can't control it – it's hugely inconvenient!"); Kelly, whose hard-as front hides a shy soul, can hear what everyone thinks about her; Simon, the introverted loner, turns invisible; Alisha, the girl who's used her looks to get what she wants, now turns men into sex pests; Nathan spends the whole of the first series feeling ripped off that he hasn't got a power – then finds out that he's immortal when he wakes up in a coffin.

"I knew from the beginning what the power was," Robert reveals. "It makes quite an impact on the second series, because it gives Nathan grounds to be far more arrogant and cocky: 'Well, I can't die, so you can all fuck off!' The immortality thing came out of his personality. He has that belief that nothing can touch him, that he's bulletproof."

Seeing Robert Sheehan goofing off between takes, you understand how he managed to stand out in Red Riding, even alongside actors of the calibre of David Morrissey, Sean Bean, Paddy Considine and Maxine Peake. He's already made the move to film, with teen drama Cherrybomb soon to be followed by Irish comedy Killing Bono and black death horror Season Of The Witch alongside Nic Cage (shot before Misfits, so he wasn't able to geek out with one of Hollywood's most famous comic-book fans. "Next time I know I'm likely to bump into him, I'm going to bring along the DVD!")

The rest are a talented bunch who make the show seem as real as possible, even when they're turning back time or stuffing corpses in freezers. It's very much an ensemble piece, with everyone taking turns to lead as we find out how they came to be picking up litter together. It's a showcase that seems to be paying off. The show's horny onscreen couple Antonia and Curtis (Nathan Stewart-Jarrett) turn out to be thoughtful drama school kids talking over each other as they run through the embarrassment of going from Shakespeare to having to "get your kit off on telly and pretend to, you know, whatever …" Antonia was recently in The Deep with James Nesbitt, Nathan popped up in the recent adaptation of Martin Amis's Money, and the softly-spoken Iwan was a potential date for Simon Amstell in Grandma's House. Lauren Socha (Kelly) might have been the first to leave ITV1's icy reality show 71 Degrees North, but she had a far grittier arthouse start in Samantha Morton's The Unloved. Of all the Misfits, she's the one who seems most bowled over by the experience. "It has completely changed my life – I have to pinch myself, thinking 'God, am I really Kelly out of Misfits? I'm in Misfits!'"

When they're not beating each other up in the community centre, they're filming on the same Thamesmead estate that was once home to another iconic gang of British screen troublemakers – Malcolm McDowell's Clockwork Orange droogs. The current residents don't seem to mind. "I think originally they didn't know what to make of us," Robert smiles. "They saw us with these jumpsuits on, walking around, basically picking up litter. I think they thought that we were making a documentary about youth crime and the state of Britain."