"It's so exciting," says Harding, 16, a year 10 student at a Sydney school. "I was jumping out of my skin when I found at school I got the part.

"We've got a little countdown calendar on the fridge - we're getting very excited in our household," she says.

Cummings's and Harding's acting skills already have the television industry talking because as a duo on screen they appear to have a chemistry that comes along only rarely.

The teenage actors were paired by chance during an audition for the Ten series, but both say it was an experience they will never forget.

"From the first moment we met in the audition room [the chemistry] was absolutely instant,'' Cummings says. ''It was amazing. We spoke about Sue and Debbie being close - they kind of had one mind - and I think Brenna and I are a bit like that as well. There's just that understanding."

"It's one of the most interesting auditions I've ever done," Harding says. "We let loose and went a bit crazy. I was really belly-laughing.

''I think the director must have seen that and perhaps that's why we ended up with the parts. It meant the connection between Sue and Deb was a lot easier on screen," she says.

Nineteen-year-old Cummings plays the character Debbie, who in the original book by Kathy Lette and Gabrielle Carey was 13. But in the television show, the age of the girls is "unspecified".

Cummings acknowledges with a chuckle, though, "I do look pretty young."

"The [characters] are a lot younger than I am, but it was kind of refreshing to go back to that childlike state and have that same looseness of the body and the enthusiasm that can be so easily expressed, without any inhibitions," she says.

Harding agrees it's a little bemusing still being an everyday Australian teenager herself, with Puberty Blues about to air on screen.

"It's interesting because it is set in the '70s, but it is just completely relevant to me, going through all the same issues and having to make all the same choices," Harding says. "It's been really valuable. It's a completely entertaining show, but at the same time it's completely relevant to kids these days. I'm sure my friends will love it."

Despite her spot-on performance as Debbie, the impish beachside teen, Cummings was actually born in Saudi Arabia and moved to Australia when she was 12. "I do have recollections of being utterly confused by this new way of life," she says.

After training as a ballet dancer until 14 - "I did ridiculous hours of dancing a week" - Cummings says she joined an acting agency because her school encouraged all performers to have a number of skills under their belt.

"I had a few auditions and fell into acting and it just took off from there," she says. An adrenal illness affected her dancing, so she turned to acting full-time. "[My passion] shifted overnight," she says.

After Cummings and Harding were chosen for the roles, the show was filmed in and around Cronulla Beach and on site at Caringbah High School.

Cummings says it was weird, but wonderful, coming face to face with Kathy Lette, one of the writers (and original teenagers) behind the book, during a set visit from Lette.

"It was really surreal because everything we were doing came from this woman's life and this woman's head - and Gabrielle Carey's, obviously," Cummings says. "So it was pretty odd."

She says Lette expects the controversy surrounding the book to reappear with the airing of the new series.

"She gave us handy hints for dealing with the media and maybe the controversy that would come with the release of the show," Cummings says.

"We didn't have a lot of time to chat but I asked her, 'Is there anything we can do to better our performances?' But she was pretty positive about it all."

Puberty Blues airs Wednesday at 8.30pm.

All in the family

Sonia Kruger is about to prove her worth at Channel Nine, with the new, rebooted series of Big Brother expected to take off with audiences.

Perhaps it helps her cause that there is a whole generation of children (and young teens) who never saw the show the first time around.

"A couple of my girlfriends have 10-year-olds now and they've all been saying to me they've had to explain, because their kids are going, 'What is Big Brother?'

"So there is a whole new generation for it," she says of the potential audience. "And then there are fans of the original show. But I'd love to see it appeal to even people my parents' age, because the casting is a lot broader."

Kruger says she watched every season of Channel Ten's Big Brother when Gretel Killeen was host. "I was hooked,'' she says.

"I like not having to think about what to turn on.

I really like it when you just know, at 7pm, that's where you're going."

Kruger says she is aware how much flak Killeen copped in the hosting role, and she is prepared for it herself. "It comes with the territory," she says. "It will be really interesting to see what happens."

Kruger will continue her role on Mornings with co-host David Campbell (their viewer numbers have been climbing lately) but will be replaced by a guest host for the show on Monday and possibly Tuesdays because of her Big Brother commitments.

She is looking forward to the challenge of making the new Big Brother work.

"No risk, no reward," Kruger says. "I get bored when I'm not pushing myself. This will be the ultimate test."

Big Brother airs tomorrow at 7pm.