Amazing adventures continue in the treehouse

That treehouse just won't stop growing.

In the books by Andy Griffiths and Terry Denton, it's up to 104 storeys. The stage adaptations aren't far behind: The 91-Storey Treehouse is coming to Canberra soon.

Andy (played by Samuel Welsh), Terry (Teale Howie) and their neighbour Jill (Freya Pragt) have new adventures and face fresh challenges as their journey continues.

During one of their adventures in a recent performance, Howie says an audience member provided a hilariously unexpected moment.

In one of the storylines, Andy and Terry come across a big red button. Terry wants to push it ("he thinks it might be amazing") but Andy is more sceptical and cautious ("It could blow up the whole world").

As the pair are discussing the issue, Howie says, an impatient voice from the audience yells "PUSH IT!"

"He said it really loudly and really aggressively."

It gave the actors a good laugh afterwards when they went backstage.

Another storyline concerns Andy and Terry being asked to babysit Alan, Alice and Baby, the three grandchildren of their publisher, Mr Big Nose, who is going to the opera with his wife.

The kids go missing, no surprise. Why would anyone entrust children to this pair?

"That is a very good question," Howie says.

"I'd like to know."

As with so much else in this series, it's best just to go with it. And things get even weirder.

And in the third strand, Andy and Terry meet the fortune teller Madame Know-It-All (Danielle King) in the hope of finding out where the children are. But what they don't know is she's a nasty piece of work.

"If you ask her questions she will drain all your knowledge and intelligence."

And that's just what happens to the boys, putting them in a zombie-like state.

Can Jill save them from this terrible fate? And how do such disparate items as a desert island, a giant spider and a submarine sandwich figure in the action?

Millions of young readers in Australia and internationally will know the answers already, having followed the characters' surreal adventures as the treehouse gets higher and higher.

But it doesn't seem to have stopped audiences from enjoying the Treehouse books on stage, with a combination of action and imagination to give the tales another dimension.

Howie says Terry, named after the books' illustrator, is a lot of fun to play.

"He's creative ... but tends to get distracted very easily."

He also played Terry in the previous production, The 78-Storey Treehouse, and says that show had a lot more conflict between the two central characters.

"In this show it's much more toned down - it's more of a buddy show."

And neighbour Jill has a crucial part to play.

Howie, interviewed during the show's Sydney season on its three-month tour, says the young audiences have been "on the edge of their seats" and highly involved in the action (as the aforementioned young catcaller shows).

"There's a lot of calling out - sometimes we encourage it, sometimes it just takes over."

Although the target audience is six- to 12-year-olds, Howie says there's enough humour for older children and adults to enjoy, too.

Howie was born in Mackay, Queensland and had acting ambitions from an early age. He played Ryan in his high school's production of High School Musical and went on to complete a Bachlor of Theatre (Musical Theatre) at the Central Queensland Conservatorium of Musical.

Since then his credits include two seasons of Bare: A Pope Opera and playing General Schmitz and a Wickersham Brother in Seussical.