Some members of the crowd sang Stand By Me - a song the couple chose for their wedding service in May.
The Duke and Duchess of Sussex arrived at Dubbo's Victoria Park to thunderous rounds of applause as the heavens opened over the drought-stricken city.
Williams, who has been friends with Meghan for several years, launched her fashion line, called "Serena", earlier this year, and describes the brand as "strong, sexy, sophisticated clothing".
The boy also had a play with Harry's beard.
However, pupils from Trinity Grammar, who have been involved with the programme, forgot to tell them about the noise generated when the cars started.
If there's anything the two have shown in the course of their tour thus far, it's that they know how to go with the flow no matter what arrises.
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Promoter De La Hoya told ESPN: "Canelo is the highest-paid athlete in the world". I'd love to have the opportunity to prove myself at this point in my career.
The couple's more-than-two-week official visit will take in multiple stops in Australia, Fiji, Tonga and New Zealand - all parts of the Commonwealth, a group of predominantly former British colonies.
"You're gonna get me in trouble", Harry joked as he embraced her.
"I'm not sure I will be good", she said, before giving it a go. That's a pretty incredible thing for anybody to do.
Pregnant Meghan, 37, cooked the delicious treat in the kitchen at Sydney's Admiralty House, the mansion home of the Governor-General of Australia, on Tuesday night following her first full day of engagements during the royal tour.
The Duke and Duchess also recently revealed that they have adopted a second dog - a black Labrador - together along with Megan's rescue beagle, Guy.
The couple had lunch at the social enterprise restaurant Charcoal Lane, prepared by young indigenous chefs.