So completely does Steen Raskopoulos inhabit his creations, that he sometimes gets stopped on the street. 'I've been muttering to myself and not realised,' the Australian admits. 'When I'm constructing a character, I'm really in my head and not able to sleep until I'm satisfied with a voice or physical trait. I'll be hunched while walking, just talking to myself, acting out the sketches. I look like a schizophrenic and a lot of people have been worried about me.'

The 30-year-old's wife and friends accept it as part of his creative process. 'But when I first started, they wanted me to get help'. Raskopoulos was nervous before his first Edinburgh Fringe in 2014. But he needn't have worried, securing a Best Newcomer nomination for his character-sketch improvised comedy, with crowds appreciating the good-natured, playful energy of his audience interaction. 'I no longer need to explain that no one should be scared, that everything comes from a place of love and joy,' he reckons as he approaches his third festival. 'I also find the UK more accepting of what I do, just because there are more sketch and improv and amazing character comedians around, I guess.'

For his new show, The Coolest Kid in Competitive Chess, he asks a 'volunteer' to engage him at the chequered board, while elsewhere he becomes a peculiar driving instructor, a grieving horse, and a human resources co-ordinator expressing himself through interpretive dance. His most popular characters serve the show, rather than the hour acting as a spotlight for them.

For the first time, there's no return for Greek Orthodox priest and movie reviewer Yianni Kostopopoulo, but stoic schoolboy Timmy Zegamo is back. With a wavering voice Raskopoulos stole from family videos of his wife as a child, he won't expand on what's in store for the pathetic poppet, beyond suggesting that 'it's a nice resolution for a lot of stuff I've set up in previous shows. It's probably the darkest show I've written to be honest and the most narrative. With the ending, everything all loops together, which I find satisfying and hopefully the audience will as well. Tonally though, some bits are pretty, pretty grim.'

He'll also be performing in The Bear Pack with his improv partner Carlo Ritchie. Raskopoulos appears in the Australian version of Whose Line Is it Anyway?, but this is a longer form improv format in which he and Ritchie simply elicit suggestions for a location and their characters' occupations, then make the rest up. He likens these 'yarns' to the film The Princess Bride, in that one character will tell the story from say, a child's bedroom, and they'll keep 'cutting away' to perform it.

Urged to bring the show to Edinburgh by Sara Pascoe and Nish Kumar, it's being produced by Liam Williams' fledgling production company Fight in the Dog: 'we're excited to hopefully get a bit more exposure and it remains one of my favourite things to do in the world,' he enthuses.

Last year's debut run of The Bear Pack was 'draining' but a 'good boot camp', he recalls. 'We found out pretty quickly that we couldn't get away with stuff that we usually can back home, so we had to really work hard. And I think we actually got better.'

Collaborating since 2012 when Raskopoulos taught his so-called protégé improv in Sydney, he maintains that Ritchie is one of the most interesting people you'll ever meet: a multi-linguist who's written a children's book in the Germanic language of Wymysorys, despite it only being spoken by approximately 70 pensioners in Poland.

The Bear Pack don't rehearse or even warm-up beforehand and never go in with anything pre-conceived. They've become so intuitive as a double act that they invariably attempt to disrupt and destroy each other's comfort zones.

'You can see us testing each other,' Raskopoulos reflects. 'Whether it's planning games within the show, trying to force the other to sing a German or Polish song or speak in poems and rhyming structures, we make it extremely difficult for each other. You line them up for an epic fail. But it's very much tongue-in-cheek and ultimately supportive. Carlo, brilliant as he is, always succeeds and gets the biggest cheer of the night. I can't explain how much trust I place in him as a performer and how much fun it is working with him.'

Steen Raskopoulos: The Coolest Kid in Competitive Chess, Underbelly, Cowgate, 5–27 Aug (not 14), 8pm, £11.50–£12.50 (£10.50–£11.50). Previews 3 & 4 Aug, £7.
The Bear Pack, Underbelly Cowgate, 15–27 Aug (not 21), 10.40pm, £10–£11 (£9–£10).