When Grace Jones was six, she loved singing along with The Wiggles to her favourite childhood song Hot Potato.

Now 23, the registered nurse has been labelled a hero for saving the life of original Yellow Wiggle Greg Page, after he suffered a heart attack on stage on Friday night.

"I don't really think of myself as a hero," the Royal North Shore Hospital nurse said.

"I've been trained to do that and I kind of flicked a switch. I went in and I just used all the knowledge that helped him, and saved him."

Ms Jones, who lives in North Ryde, was on a nostalgic night out with her family, including her five siblings, at The Wiggles bushfire relief concert at the Castle Hill RSL when Page, who co-founded the iconic band in 1991, collapsed on stage on Friday night.

He had been feeling unwell before the charity performance but had decided to push on with the show.

The 48-year-old performed up to the last song of the night before collapsing at the side of stage. Neither the crowd nor the band realised how serious the situation was, with the band playing another song.

Once it became clear, Blue Wiggle Anthony Field asked the crowd to leave. Without a second thought Ms Jones, dressed in a Wiggles T-shirt, asked a security guard if they needed medical assistance and headed backstage.

She found drummer Steve Pace and crew member Kimmy Antonell performing CPR.

"I just walked in and I was the only one there with any training beside first aid training. So I started doing what I do at work," she said.

She used a defibrillator to shock Page three times, a move NSW Ambulance said helped save his life.

By the time intensive care paramedic Brian Parsell arrived, Page was unconscious but had a heartbeat.

He had suffered a blockage in one of the major blood vessels in his heart, which caused a cardiac arrest, Mr Parsell said yesterday.

"Had the team on stage not commenced CPR, had Grace not had the courage to use that defibrillator, then we may have been dealing with a different outcome," he said.

"The hero of the story here today is Grace."

On her way out to reunite with her own family, Ms Jones reassured Page's parents, who had watched him collapse, that their son was going to be okay.

"She has always been very capable and a strong individual," her father Graham Jones said.

"She was anxious for what happened to Greg and I guess the emotion started to come out then, but she was fine. I am very proud of her."

Ms Jones' willingness to help comes as no surprise to her family; the UTS graduate's mum and two grandmothers were nurses.

Page was in a serious but stable condition at Westmead Hospital last night. From his bed, he gave his blessing for another charity show last night.

"He didn't want to let all the fans down, which is surprising considering he is in a hospital bed," show director Ben Alcott said.

Fellow original band member Anthony Field became emotional as he told the crowd at last night's second concert that Greg remained in a stable condition in hospital.

"I saw Greg today in hospital and he's doing really, really well. He said you have to do the show tonight," Field told fans.

"Let's raise the roof tonight and do it for Greg whilst raising funds for the Australian Red Cross and WIRES."

Original band members and special guests donned yellow skivvies in Greg's honours including Paul Field, Paul Piddick, Emma Watkins and Simon Pryce.

A sold out crowd of 800 fans turned out for last night's second concert.

at the Castle Hill RSL on Saturday night to raise funds for bushfire affected communities in NSW.

Fellow band member Anthony Field told the crowd on Saturday that Greg remained in a stable condition in hospital and his main concern was that the show would go on.

"I saw Greg today in hospital and he's doing really, really well. He said you have to do the show tonight," Field told fans.

"Let's raise the roof tonight and do it for Greg whilst raising funds for the Australian Red Cross and WIRES."

Original band members and special guests donned yellow skivvies in Greg's honours including Paul Field, Paul Piddick, Emma Watkins and Simon Pryce.

Organisers said Friday's appeal concert was added by popular demand after Saturday's event sold out "within five minutes".

Fans said described the event as a "trip down memory lane"

"I've been a fan all my life and this was the first chance I've had to see them," said Lynn Carpenter, 32.

"It's disappointing Greg couldn't be here but I certainly don't hold it against him - I think we're all hoping he gets better soon."

Items auction at the concert in support of the appeal included platinum albums and signed 'wake the eff-up Greg t-shirts."

The original Wiggles lineup previously reunited for charity in 2016 to fundraise for Australia's Soldier On foundation.

At 48, Page is the youngest of the original lineup which includes Red Wiggle Murray Cook (59), Purple Wiggle Jeff Fatt (66) and Blue Wiggle Anthony Field (56).

An illness, orthostatic intolerance, forced Page to retire from the band in 2006. He rejoined in 2012 but he, Murray Cook and Jeff Fatt all retired several months later.

The original Wiggles reunited for the shows raise money for the Australian Red Cross and wildlife rescue organisation WIRES.

* Additional reporting Briana Domjen, David Barwell