They are the rock stars of children's literature, selling millions of books and attracting thousands of adoring readers large and small at events held around the world.

But Andy Griffiths and Jeff Kinney say groupies are not a part of their touring schedule.

"If only," jokes Griffiths, whose latest book in his Treehouse series was proclaimed the fastest selling Australian work of fiction in a decade earlier this year.

"Not in the sense that a rock star would have them," he adds. "You get a lot of grateful parents with tears in their eyes."

Griffiths and Kinney, author of the Diary of a Wimpy Kid series, will share a stage on Sunday at the City Recital Hall in Angel Place as part of the 2015 Children's Festival of Moving Stories.

Griffiths says he has compiled some of his favourite Wimpy Kid moments and plans to interrogate Kinney about his creative process.

Kinney, meanwhile, says he may have to go back to the drawing board with his speech: "I've heard Andy is a rock star on stage and if he's funny and I'm not, you know, then I'm in trouble here."

The audience will also have the opportunity to question both authors during the event, which is organised by the Sydney Writers' Festival.

Kinney says children are often eager to find out about new characters and plots, although in China he was asked about the symbolic importance of the number of hairs he drew on a character's head.

"I like it when a kid asks a question that's a little audacious," he says. "Every so often a kid will ask 'Are you rich? Do you live in a mansion?' And you'll see a parent bat their hand down."

Both authors agree children share similar reading interests regardless of where they are from.

"You enjoy topsy-turvy humour," Griffiths says. "You're in a world where the adults are ruling things and you love jokes and books that undercut that. What happens if you don't do what the adult says?"

Kinney is travelling the world to promote Old School, his 10th Wimpy Kid book, which he says is a change of pace from his usual touring schedule.

"Usually what I do is tour the United States on a bus and we do seven events a day and then at night we do karaoke on the bus to blow off steam," he says.

His favourite karaoke selections are tracks by Muse, Bon Jovi and Lyle Lovett.

Griffiths says he has developed a "stand-up comedy schtick" during two decades of touring schools as a visiting author.

"I've always loved winding children up, telling them something silly and seeing how long you can do it before they say 'That's not true'," he says.

Kinney says many children's authors like Griffiths or David Walliams are "born performers". "And I definitely am not. My style is probably overly earnest."

Asked by Griffiths if he enjoys live shows, Kinney says: "I don't mind getting up on stage. If you're on a stage, it means you're doing okay in life and that's pretty cool. But I don't have the knack for it that I think a lot of my contemporaries have."

Griffiths continues work on The 78-Storey Treehouse, which he will hand over to collaborator Terry Denton to illustrate in the new year.

Kinney says he will probably add to the Wimpy Kid series, and come up with more adventures for his protagonist Greg Heffley.

"I'm not trying to compare my self to [Peanuts creator Charles M] Schulz but if he tried to spread his wings I'm sure he would have been batted back down and told to go back to Peanuts," he says. "I have a feeling that's where I am. I have a feeling the world wouldn't like me to … they want me to keep doing Wimpy Kid books."