Can't hold a candle to Opera House's 40th Celebration for all: Four-year-old hangs her drawing of the opera house on a clothes line. The celebrations as Sydney's icon of opera turns 40 are more Dame Edna than Dame Joan, with giant cupcakes, mini Hills Hoists, bouncing kangaroos and a lifesaver for each of her years. On a brilliant Sydney blue sky Sunday morning before smoke turned it all to grey, Jimmy Barnes led a joyful thonged throng in Happy Birthday on the house steps. Then 6000 pink cupcakes were passed among the masses in a ceremony presided over by the new Opera House Trust chairman "Aussie" John (Home Loans) Symond and Greig Pickhaver, aka H.G. Nelson. The choice of Barnes to sing was deliberate. "We weren't being a high arts Opera House, we were being a people's place," David Claringbold, director, Opera House theatre and events, said. Hooray: A huge cupcake briefly stole the show, but the crowd was there for the guest of honour. The six-metre candled cupcake was only a prop. Lifesavers leapt off rubber duckies, ferrying an edible one made by chef Matt Moran the same way they would a rescue reel. Governor Marie Bashir gave a speech, as did Louise Sauvage, paralympic wheelchair racing champion and Opera House accessibility ambassador. Moran tweeted his surprise at being mobbed by the crowd. "Chefs are the new rock stars," Barnes tweeted back. An estimated 20,000 people queued to peer under the old girl's skirts, taking advantage of the Open Door morning to wander through the Concert Hall and Joan Sutherland Theatre without having to hush for a change. Memorial: Lin, daughter of late Danish architect Joern Utzon. When the Queen declared the house open 40 years ago to the tune of Beethoven's 9th, few foresaw that the future would include more than 100,000 people on the steps to farewell rock band Crowded House in 1996, a World Heritage listing in 2007, or 5000 bare bums in the name of art in 2010. Way back then her Danish architect Joern Utzon was persona non grata in Sydney after a falling out with the state government. But Utzon's son, daughter, granddaughter and great granddaughter were all here for the birthday celebrations thanks to a famous 1999 rapprochement with the since-deceased architect. Someone griped on Facebook about fireworks erupting from the prop cake during a total fire ban. But Sydney has always been ready to make exceptions for probably her best-loved and certainly most exceptional building.