The happy prince and his US-born wife laughed and smiled as they were inundated with gifts -- a pair of Australian baby Ugg boots, baby blankets, toy kangaroos and joeys -- watched eucalyptus-munching koalas at the zoo and took a boat ride across Sydney Harbour at the start of a lengthy tour of the Pacific.
"We genuinely couldn't think of a better place to announce the, err, upcoming baby... a boy or a girl," said a hesitant Harry, as he toasted his Sydney "mates" and lauded an afternoon reception for serving both tea and beer "in true Aussie style".
Meghan began the day wearing a tight white dress by Australian designer Karen Gee and showed few signs of having a baby bump, to the mild disappointment of onlooking fans.
But she smiled broadly while posing against the backdrop of the Opera House sails, which gleamed in the spring sunshine.
Shortly after the appearance, Gee's website was down, apparently due to the volume of traffic it was receiving.
- Media frenzy -
At the foot of the Opera House a crowd of hundreds pressed against security fences for a royal outdoor meet-and-greet, waving Australian flags, assorted pictures and carrying human-size koala toys, all under the gaze of police snipers and close protection officers.
"To see them in the flesh was amazing. You can't describe it," said 53-year-old Tanya Galway. "I climbed up that pole there to get a better view."
The royal baby was on the mind of most of the crowd, including 56-year-old fan Rhonda Tissington, who managed to give the couple a gift.
"I quickly put together a baby blanket and a first baby book, of farm photos inside," she told AFP. "Harry said 'Oh wonderful', so he was very pleased. He even shook the present."
This royal couple are on a 16-day tour of Australia, New Zealand, Fiji and Tonga that had already been keenly watched but is now set to be a media frenzy that may test Australia's large contingent of royal-sceptic republicans.
Shortly after the pair stepped off the plane on Monday, Kensington Palace announced that Queen Elizabeth II's 34-year-old grandson and the 37-year-old actress are "expecting a baby in the spring of 2019", triggering a chorus of coos and rampant tabloid speculation about baby names.
"What fantastic news!" tweeted Australian Prime Minister Scott Morrison. "Australia is thrilled for you both. Looking forward to sharing in the joy during your stay down under."
The queen was said to be "delighted", British Prime Minister Theresa May tweeted her "warmest congratulations", and Meghan's mother Doria Ragland said she was "very happy about this lovely news".
As TV stations in the English-speaking world broke into their regular coverage, Google saw a spike in searches for "when is spring?" -- the answer in Britain is from March until May or June -- and newspapers mused over what the baby, who will become either an earl or lady, will be called.
The bookies' instant pick was Diana -- the name of the late princess who was mother to both Prince Harry and his older brother Prince William -- along with Arthur and Alice.
The celebrity couple can expect a warm welcome on their tour, even if polls show half of Australians would like to ditch British monarchs as their country's head of state.
- American princess -
Kensington palace said they did not expect any changes to the trip schedule, although Meghan is not expected to join Harry in scaling the Sydney Harbour Bridge to mark the start of the Invictus Games later in the week.
They are still expected to visit Fiji and Tonga despite a notice advising pregnant women to stay away because of the Zika virus.
The decision came after consultations with doctors, Kensington Palace said.
Meghan made her name in acting as savvy paralegal Rachel Zane in the US television legal drama "Suits", a world far removed from Buckingham Palace.
Her first steps as a British royal have been cautious, immaculately scripted and well received.
Britons swooned after seeing Meghan nonchalantly closing her own car door at her first solo engagement last month in London.