Down on his luck, an insecure Marek Larwood self-Googled, only to find that the top search query was 'Marek Larwood retarded'. As one-third of the acclaimed, anarchic sketch trio We Are Klang, he's accustomed to 'talking ball-bag' and 'Gollum after he's been hit with a spade'. But this crystallised why casting directors were only seeing him for the most oddball acting roles. It could have been worse though. He used to be a sex offender called Brian.

'I'm glad you called him a sex offender,' he enthuses. 'Because a lot of people used to say, "what was that paedophile character you did?" At no point did I make paedophile jokes. I found myself robustly defending Brian: "I think you'll find he's a sex offender!" It's one step up I suppose.'

A victim of his own, highly-qualified success – 'I never played idiots until Klang' – collaborating with the 6'8 Greg Davies necessarily thrust the 36-year-old into a low-status role. Emerging now, blinking, from beneath Davies' considerable frame, his debut solo hour, Typecast, opens with a montage of his most embarrassing onscreen episodes. 'Initially, it was far too long at two minutes,' he states. 'But even that was about 100 different humiliations. Literally covered in crap, smashed around the face, hit by chairs. That's my career to date.'

Trailing way behind Davies and third Klanger Steve Hall in performing solo at the Fringe, 'things have gotten pretty desperate. I tell you what mate, I've been fucking unlucky.' Popular CBBC sketch show Sorry I've Got No Head was axed last year, while the Channel 4 pilot Felix & Murdo – starring Armstrong and Miller as dissolute 1908 Olympians with Larwood as their eccentric butler, was underwhelming. An equally low-key affair was BBC Two's talent-packed improv showcase Fast and Loose, a fact he attributes to over-earnest editing, the show not being anywhere 'loose' enough and the director's impatience with him, 'pointing at my dick all the time, just to make Greg laugh. Honestly, I have this preoccupation with pigs and dicks. I'm like a four-year-old with Tourette's. It's a bit embarrassing, a regimented illness manifesting itself on stage'.

Larwood describes Typecast as, 'not really stand-up, but quite odd and the most Klang-like' of the trio's endeavours so far. He hopes to work with Hall and Davies in the future but Klang is dead, killed by a couple of lacklustre TV adaptations. 'We were so much better live,' he sighs. 'We didn't know what the fuck was going on with the first series and trusted people who seemed like they did. It's time to find work again.'

To this end, he's making a silent pilot for Comedy Central called Mr Shush, but before that he's shooting the BBC Three prank show Impractical Jokers around London and the Fringe with fellow comics Roisin Conaty, Joel Dommett and Paul McCaffrey. Guided via earphones into interacting with an unsuspecting public, 'I'll be rushing round Edinburgh making a twat of myself, then rushing back for my show. Performing comedy is the road to mental.'

Marek Larwood: Typecast, Pleasance Courtyard, 556 6550, 4–26 Aug (not 14), 6.20pm, £10–£12. Previews until 3 Aug, £6.