"Gee, Howard – this bit where it says, 'He pisses on her tits' – can we smooth that?" "Oh sure, how about if he says, 'I'm going to eat jelly off her tits'? They fucking loved it!"

It's not until Howard Overman starts laughing about toning down some of the "coarser, rougher edges" of Misfits for the US version that it's possible to reconcile the wild and often filthy streams of consciousness he's written for his asbo superheroes with the polite chap sitting in a Hove pub drinking grapefruit and soda.

Over three series of Misfits, he's hit on a rich seam of youth culture: putting characters who are "going out, getting laid, doing what people in their 20s do" into outlandish situations – but then making sure that their reactions are real, running a gamut that includes disbelief, freaking out and, well, boredom. Not a lot of that gung-ho, "Ooh, great powers, great responsibilities, must save the world!" stuff that seems an intrinsic part of the chemical balance of any American teen in the same unlikely situation.

Misfits is very much a show of its time – it both looks and sounds great, thanks to some gritty cinematography and a soundtrack that runs from a theme tune by the Rapture back to the Velvets – and since it won the Bafta for Best Drama in 2010, it's fair to say Overman has been on something of a roll. He's worked with US pop culture guru Josh Schwartz (The OC, Chuck, Gossip Girl) on a pilot for a New York version of the show, he's sold his first screenplay to Sony Pictures ("A comedic take on Terminator"), he's started work on the fourth series of Misfits for E4 (due back before summer), and now he's meeting the Guardian to talk about his "holistic detective" Dirk Gently as it returns to BBC4 for a three-part series this week.

It's fair to say that Gently is something of a shift from the Thamesmead teens – swapping lines like "What the fuck is brunch?" for a more stylised tone, incorporating Gently's wild flights of intellectual fantasy, where he riffs on "the fundamental interconnectedness of all things" and drinks a lot of tea.

At the heart of both programmes, however, is an understanding that when you've got "ridiculous things happening" (zombie cheerleaders, alternative Nazi timestreams, robots stalking Cambridge) you've got to persuade an audience to "go on a ride with you" by making the characters feel "of their time and place". Even Misfits' early twist on the superhero genre – a lightning storm that gave people powers that reflected their personalities – served to ground the story rather than feeling like an excuse to get a bunch of effects shots on screen.

Dirk Gently is based on a series of novels by the late Douglas Adams, the cult author behind The Hitchhiker's Guide To The Galaxy. Overman first "read and enjoyed" the books, a kind of freewheeling riff on the Sherlock Holmes model, when he was 17, and saw "great potential in the character" of "holistic detective" Gently when he came back to them some 20 years later. As he points out, whenever you're writing a detective story it's hard to out-clever Holmes, or to come up with a "unique detective methodology" – but in Adams's tea-drinking agent of chaos he saw a fresh and different take that could work as an ongoing franchise.

'Doing a straight cop show doesn't hold any appeal for me … There's not much TV that doesn't benefit from a bit of humour'

Dirk Gently. Photograph: Des Willie

The 2010 pilot with Stephen Mangan, Darren Boyd and Helen Baxendale set the tone: more translation than straight adaptation, taking only some of the elements from the novels – like Dirk's belief in "solving the whole crime" and his refusal to pay his secretary, Janice, so that she'll keep turning up – and updating them. This may be because, unlike Sherlock, there are only three works to draw on – Dirk Gently's Holistic Detective Agency, The Long Dark Tea-Time Of The Soul and the unfinished The Salmon Of Doubt – so pretty soon, you've got to write new cases; for another, the budget wouldn't stretch to bringing some of Adams's more fantastical elements to TV, such as the Electric Monks or a sofa stuck in a hallway thanks to a time paradox.

The budget did, however, encompass an Austin Princess for Dirk (Mangan) and assistant ("Partner!") Macduff to drive. Part "piss-take" of Inspector Morse's Jag, and part nod to Overman's dad who drove one (and would joke about how "changing gears was like playing Russian roulette"), it's a very British detail that adds to the overall sense of chaos – especially when you see their "zen navigation" version of a "follow that car!" moment: driving after whoever is in front of them in the blind hope that they'll end up where the case needs them to be.

Overman's career path has been convoluted, too. Ditching office life in "various crappy project manager and marketing jobs, all of which I was rubbish at" for script-writing ("I hated having to make conversation with people I didn't like") Overman worked on Hotel Babylon, New Tricks and Merlin, but it was only when he came up with his "Skins meets Heroes" concept that he made a mark. Misfits was well-placed to capitalise on a more receptive commissioning environment after the successful reinvention of Doctor Who and a mainstream hit like Life On Mars – itself a hard sell that famously languished in development hell for years before BBC1 jumped in.

As Overman knows, it wasn't always easy to convince people to take a punt on high-concept scripts like "time-travelling cop". "I can remember pitching an idea before Life On Mars – except my guy was a dentist. Like those 80s shows like The A-Team where they'd go around helping any old fucker, the idea was that he'd help people because he was plagued with guilt; his wife had died, he caused the crash, you didn't know if he was alive or dead. At the time they couldn't get their heads round what I wanted to do. I might resurrect the idea next year. Now they'd probably all go, 'Oh yeah! A dentist!'"

If there's a thread tying Overman's work together, he's says it's finding "a comedic take on genre". For example, his film, The Slackfi Project, is about an ordinary guy working in a coffee shop, where two guys show up and tell him he's got to save the world – what Overman refers to as "sci-fi now", a clash between sci-fi and the norms of conventional life.

"I like the structure of genre and the complexity of the stories; they're big, dramatic stories that take you into another world. I have a tendency to not take things too seriously, so I undercut it with a bit of comedy. Doing a straight cop show doesn't hold any appeal for me. 'Did you do it? No I didn't' – it's a long 60 minutes. There's not much TV that doesn't benefit from a bit of humour – even something like The Sopranos – it's really funny in moments. Tony's girlfriend will throw a big steak at him and it will just hit him in the face – that's real Tom and Jerry – yet it's in the context of a plot which turns quite nasty. Sometimes 'serious British drama' almost fails to have any humanity on some levels because you can't live your life that earnestly; 'this is life or death' all the time. Even in the most dire situations people tend to crack jokes and muck around, and there are very few dramas that can't be improved with a bit of humour."

Dirk Gently, Mon 5 March, 9pm, BBC4