Hollywood heavyweights Robin Williams and Kevin Klein are among those who have handed over their jeans to the talented caricaturist for the charity's annual jeans auction.

But this year it was the star of blockbusters such as Superbad, Knocked Up and The Wolf of Wall Street - Jonah Hill - who got to be depicted in denim.

"This is my 21st pair of celebrity jeans and so this year I tried something completely left of centre," Mr Dorin said.

"Instead of just using the pair of jeans as my canvas, I used the jeans as part of the artwork. So I got a big sheet of masonite and drew a caricature of Jonah wearing the jeans.

"It's a bit of a break away from what I've done before but I'm very happy with the end result."

Mr Dorin said he used Hill's character - an underachieving cop - in the movie version of 21 Jump Street for inspiration.

This year marks 21 years of Jeans 4 Genes and Dorin is the only artist who has contributed to the painted jeans auction since its inception.

In the process he's helped to raise more than $100,000 for research into birth defects and childhood diseases such as cancer, epilepsy, and a range of genetic disorders.

"I've done the jeans of Hollywood actors but also of Australian celebrities like TV presenter Jules Lund and sporting stars like Ricky Ponting, Brad Fittler and Craig Lowndes," he said.

"They've all done well at the auction, with Lowndes' jeans attracting the highest bid of all my jeans, at $10,000.

"I became involved in Jeans 4 Genes before I had kids because I thought it was a great cause, but since having kids I'm even more connected and committed to it.

"Each year when I'm putting blood, paint and tears into the project I say it's going to be my last year, but then when I get the phone call to take part again I know I won't be able to say no."

The jeans, along with painted pairs from other celebrities, will be auctioned off at Jeans 4 Genes Day gala dinner in Sydney on August 23.

For more information, see jeansforgenes.org.au