Arj Barker is fretting about a cannon. The Californian standup hasn't been to Edinburgh in 10 years, and he's forgotten those local touches that can make the Fringe so, well, explosive. "Last night, during one of my jokes, in that perfect little space between the setup and the punchline, a cannon went off," he says. Barker's show, it transpires, coincides with the Military Tattoo in the castle, yards from his venue. "It was one of the biggest cannon explosions you can imagine. The audience laughed, I laughed – but that's going to happen every night." He furrows his brow. "When we booked the gig, I was like, 'Jeez, I wonder why the 9.20 slot is available?'"
Barker, now 35, has arrived in Edinburgh wreathed in glory: having starred in what many people see as the world's hippest sitcom, HBO's Flight of the Conchords, he is now returning to the city where, in 1997, he bagged a Perrier best newcomer gong. So you might think he could laugh off the obtrusive military hardware. But Barker's angst is the real thing. His signature style, both as a standup and as his TV alter ego Dave Mohumbhai, may be spaced-out slacker cool – but, in conversation, a fretfulness lurks, barely concealed beneath the easy-going San Francisco drawl.
He's also downbeat about his achievements and tentative in expressing his opinions. One discussion of the dynamics of Flight of the Conchords show tails off when Barker concludes: "I don't claim to know anything about anything, really." If this humility stems from a sense that his is just a minor role in someone else's success, he should give himself a break. Yes, the stars of Flight of the Conchords (another comedy act forged on the Edinburgh Fringe) are undoubtedly the Conchords themselves, played by Jemaine Clement and Bret McKenzie. But Barker – as the show's know-all, know-nothing pawnshop assistant, dispensing gnomic advice about women and America – appears in almost every episode and is (alongside fellow standups Kristen Schaal and Rhys Darby) one-fifth of the idiosyncratic quintet that made the show so kookily enjoyable.
Barker plays down his contribution. "I'm like a dumb Yoda in the show," he says. "I just pop up and say a few things." But he admits he wouldn't be in Edinburgh without it. By the time he had clocked up four festivals, he had lost his Fringe mojo. A relationship breakup drove him away from the UK, where he had settled, and into the arms of Australia, which has since become "by far my most fertile market".
He returns simply to capitalise on his Conchords success. "I even considered naming my show Oh My God, It's Dave from Flight of the Conchords," he says. Why didn't he? "Half of me thought, 'That's too silly.'" Is he scared of seeming to hang on the Conchords' coat-tails? "No. But I don't expect Flight of the Conchords fans to know Arj Barker is the guy who plays Dave. I need people to go, 'I know that guy, he's funny on that show. Let's go see his standup.' Making that connection: that's been the challenge."
None of this was an issue when Barker first came here in the late 1990s. A standup upstart from San Anselmo, California, he made an instant impact with his blissed-out surrealism. Edinburgh seemed like a home-from-home: Barker was weaned on Monty Python, although he also cites a less likely influence. "I remember one Two Ronnies joke," he says, "which I re-enacted as a child at summer camp. It was one of their fake news items. A robber steals 2,000 eggs, 4,000lbs of chives and 1,500 onions – and police are now looking for a 40ft omelette. I went onstage and said that. And my dad came out dressed as an omelette, with a yellow tarp over him and green shit taped to it. I loved that joke."
The dad in question is Sikh, but Barker doesn't trade on ethnicity in his comedy. "I did one or two gags early on about that, because making jokes about your heritage was the thing to do. There were a few gags – I'm not proud of them – about how my dad worked at the 7/11, all that Indian stereotype bullshit." But he felt it didn't ring true. "I'm not hiding my ethnicity. It's just that I was raised in a California environment, with mostly white kids but also kids of different ethnicities – and there was never a racial divide. We all sounded the same and we never really thought about it. I never particularly felt like an Indian kid." But he did change his birth name, Arjan Singh Aulakh. Why? "I wanted a stage name people would pronounce correctly." Did he take the new surname from Ronnie Barker? "Maybe subconsciously," he admits.
'Banging is no longer the priority'
Armed with a new moniker, Barker prospered. Over in the UK, he befriended acts who he later saw "rise up and become monsters" of UK comedy. "Jimmy Carr and I worked on a TV idea back then," he says. "We were planning this show about an uptight, stiff English guy and a lazy Californian. I won't tell you who was going to play who." He grins. "Of course, I want to run it by him again, but these days the son of a bitch won't return my calls."
Although he's joking, he has spoken before about distancing himself from the competitive side of the comedy industry. As a young comic, says Barker, "I was like, 'I gotta become a headliner, I gotta get on TV.'" On achieving those goals, he savoured the success. Then he met Clement and McKenzie at an Auckland comedy festival in the early 2000s. "I was partying a lot and drinking," he recalls. "And chasing girls as much as I could."
In fact, Clement and McKenzie's first impression of Barker led directly to the character of wannabe ladies' man Dave: like the other stars of the show, Dave is a cartoon version of the real-life actor playing him. But now Barker has grown up. "Banging chicks," as Dave/Barker calls it, "is not the priority it was. I'm not going to say I go home and read Charlotte's Web every night after my show. I mean, I do some nights – it's a great book. But partying is not what I live for any more."
What he lives for is standup comedy. His efforts to develop an acting and/or TV career have been – Conchords apart – only patchily successful. On the one hand, his spliff-inspired theatre show The Marijuana-Logues played off-Broadway for a year. But he lost out on the lead role in a proposed Indian-American sitcom Nearly Nirvana, and he was knocked out of NBC standup contest Last Comic Standing in the early rounds. Of his performances in the Conchords show, he says: "Aside from a few chuckles and the occasional 'Hey that was great, Arj', I never knew if it was funny, or if I was up to the level of the other actors."
For now, Barker is content to be an excellent standup – on which point, his confidence is bulletproof. His Edinburgh show is, he says, "an hour of power", a greatest hits selection of jokes from the last two years. "I like to act smart," says Barker of his act, "then reveal that I'm either an asshole or an idiot." On stage, he expounds on religion, climate change and the vicissitudes of text-messaging. In conversation, he passionately defends "comedy just for the sake of being funny. I read an article in which a certain comedian said, 'I do important jokes. I don't talk about skittles.' That was the example he used, to show that he took on the issues and helped the world. Well, that's fine – but comedy doesn't have to be about anything. If you have a great joke about skittles, there's nothing wrong with that. If you made someone laugh, that's an important job in itself."
A glass-with-water-in-it person
Barker cites a current routine about gay marriage, in which he mocks the idea that homosexuality can be cured. "If I'm expressing an opinion that's important to me, that's just a bonus. My job is to be funny, and I won't sacrifice that to make a point." On this issue, if on few others, Barker is impassioned, sure of himself – and so dedicated to getting his standup right that I begin to understand why a booming cannon might bother him. "I'm confident because I know I'm a good comic, but I'm not confident everything is going to go my way all the time."
Seemingly channelling his Dave Mohumbhai character, he adds: "As opposed to being a glass-half-empty or a glass-half-full person, I'm more like, 'Oh, there's some water.' But I'm making a living doing what I want to do. I have my health. I have freedom. I could go anywhere in the world and do standup. I want to be more forgiving of myself, live a normal life and try to do good shows. I don't want to be a tortured comedian."
• Arj Barker is at the Assembly Rooms (0131- 623 3030), until 29 August.