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The 48-year-old Greg Page, known to Australians as the original Yellow Wiggle and an intermittent member of the group since its beginning in 1991, fell in front of fans while walking off stage at the end of the concert.
"As has been reported, our friend Greg Page suffered a cardiac arrest at the end of the bushfire relief performance and was taken to hospital," The Wiggles said on the band's Twitter account.
"He has had a procedure and is now recovering in hospital."
Musicians, artists and sports personalities have held a number of relief events to help Australians who have been battling deadly bushfires since September. The fires have killed 29 people and millions of animals, and destroyed homes and large swathes of land.
The Wiggles have sold millions of records in Australia and abroad. Page, the lead singer, founded the band with a group of friends from a university.
He has spoken about suffering from orthostatic intolerance, a disorder that affects blood flow and leads to fainting, according to media reports.
Friday's reunion performance was to benefit the Australian Red Cross and the New South Wales Wildlife Information Rescue and Education Service.