G-whizz! Gina makes Chicago debut

Kath and Kim star Gina Riley may have swapped TV for the stage, but there is a chance her famous G-string could make its debut on the saucy Chicago set.

Riley, best known for her portrayal of self-absorbed Kim in the hit TV comedy, has gone back to her singing roots and is playing the corrupt prison Matron "Mama" Morton in the hit musical.

Although there is an enormous difference between acting on TV and performing in a musical, Riley, who usually writes, produces and acts, says it is good to step back and be part of the pack.

"It's quite different to come back and just be an actor - it's great," Riley told AAP after belting out a show-stopping song on stage at Lyric Theatre in Brisbane.

"I'd been looking to do something where I wasn't driving the bus."

She revealed that the American choreographer and musical director had given her some control of her portrayal of Mama Morton.

"I was a wondering how I was going to go ... once they've got to know me, they've given me free rein to do what I like - within the concept of the show."

She denied rumours circulating on social networking site, Twitter, that she has a broken ankle (as she twirled her ankles in circles).

"We've asked Twitter to take that down, it's not me, someone's impersonating me, my ankles are fine," she said.

After five weeks of rehearsals, Chicago kicked off its national tour in Brisbane on Thursday night, with Riley joining the likes of Caroline O'Conner, who plays Velma Kelly,

Craig McLachlan as Billy Flynn and Sharon Millerchip is Roxy Hart.

Riley said the opening night was great and the show "ripped along".

"As a performer it's very naked," she said of the raunchy show's dressed-down set.

"We're all in black - it's just about the performers - and there are some incredible performances in this."

And when asked if her famous "Kim" G-string would be on show, she laughed: "You never know - maybe for the occasional matinee."

Once she finishes touring with Chicago, Riley reveals she and "Kath" - Jane Turner - will start writing again after an extended break.

"Once this show's finished we'll start writing and see what happens," Riley said.

Riley said she wasn't sure if the US version of the show was still running, after critics savaged the NBC production.