William Shakespeare didn’t believe the younger generation could cheerfully rub along with their elders and betters. As he wrote in ‘The Passionate Pilgrim’: ‘Crabbed age and youth/ Cannot live together/ Youth is full of pleasance/ Age is full of care’. Clearly, the Bard never made it to the Fringe. Among the usual weird and wonderful assemblage of talents, this year’s arts bonanza includes a series of appearances by 12-year-old stand-up Eros Vlahos.

While his all-time comedy hero is Ricky Gervais, Vlahos feels his observational comedy, which pokes plenty of good, healthy fun at teachers and parents, was largely honed before his first audience: his classmates. ‘I used to go to a really strict school, but moved when I was eight,’ he says. ‘It was a much more relaxed environment and I kind of became the class clown after that.’

Vlahos is a graduate of the Comedy Club 4 Kids, the well-known training ground for young stand-ups set up by comedian James Campbell, and found that performing in front of large audiences came naturally to him. He was later recruited as CBBC’s resident stand-up comic, which led to him being mentored on stage as part of Comic Relief by Ed Byrne. The Irish stand-up challenged his young protégé to perform in front of 14,000 Watford FC fans at Vicarage Road during half time. ‘That was pretty nerve-wracking but everyone laughed and was so nice to me,’ he says. ‘That kind of turned me into a Watford fan.’

Over at the veteran end of the age spectrum, legendary comedian Joan Rivers is returning to the Fringe after an absence of six years with her self-penned play, Joan Rivers: Work in Progress by a Life in Progress. While the piece is set in a dressing room where Rivers prepares for what might be her last gig at the Oscars, the New York comedian says she has no plans to bow out of showbiz any time soon.

‘I’d never consider retirement,’ she says. ‘And do what? Walk around and tell jokes to the postman? I’m very lucky because I’ve found something I like to do and I can make a living doing it. You can get older and uglier as a comedian and it doesn’t matter. I have so many friends that are actresses and they can’t get arrested any more. I don’t think about my birthday. When people ask me how old I’m going to be, I just stare at them and say, “Are you insane?” No way.’

Rivers will also be performing a string of stand-up shows at the Fringe. When she mentions the name of the venue (the Udderbelly) and I explain that she will be performing in a giant, inflatable upside-down cow, she doesn’t skip a beat: ‘That sounds like me.’ The years evidently haven’t mellowed Rivers’ propensity for poking fun at herself, nor her notorious waspish wit. Her latest material pours scorn on celebrity culture, reserving particularly potent measures of bile for troubled supermodel Naomi Campbell. ‘She’s so thin,’ she rasps. ‘That’s why they can’t lock her up: she would go right through the cell door. Now, you show your vagina and you’re a celebrity. You’re drunk and you run over a lot of people and you’re a celebrity. All those reality shows are full of boring people and you don’t have to have any talent.’

Having thoroughly enjoyed her Fringe debut in 2001, Rivers retains a soft spot for the Scots, and even feels we should be thankful for our wretched climate. ‘Women’s skin looks better without so much sun; that’s why Scots women are so beautiful. Look at New York; we live on doughnuts and fast foods, which is why we’re such big fatsos.’ The key to eternal youth: grey skies, endless rain and a persistent North Easterly wind.

Joan Rivers: Work in Progress by a Life in Progress, Udderbelly’s Pasture, Bristo Square, 0844 545 8252, 7—25 Aug, 3.45pm, £18—£25 (£15); Joan Rivers: Stand Up, Underbelly, Cowgate, 0844 545 8252, 12 & 13, 19 & 20 Aug, 11.45pm, £15; Eros Vlahos, Sweet, Teviot Place, 0870 241 0136, 2—17 Aug, 3.50pm, £8 (£5—£7).