Crown Prince Frederik is accustomed to some titles, among them the most popular your royal highness.
But he blushed as he responded to another on Saturday during a visit to the Sydney Children's Hospital.
"Hello gorgeous" is how adoring and self-described royalist Fay Thompson grabbed the Danish Royal's attention before pleading with him for a photo in the hospital driveway.
"I said 'hello gorgeous can I take your picture'," she told AAP.
"For an old duck, that's quite good isn't it?
Mrs Thompson hoped her granddaughter, who is a patient at the Randwick-based hospital, could have had a glimpse of Frederik and Crown Princess Mary during their visit.
"We got all her equipment and moved it to the window so she could look down but it's hard - she is so tired," Mrs Thompson explained.
Mrs Thompson shot downstairs to snap a photo on her phone to show her 10-year-old granddaughter, who had just undergone a bone marrow transplant.
The Danish Royals spent day three of their Sydney tour with the not-for-profit Australian Twin Registry and the Sydney Children's Hospital.
A small but admiring contingent of predominantly female onlookers gathered outside the hospital entrance to get a glimpse of Princess Mary.
Wollongong twins Charlotte and Lillian Harding, 8, practised their curtsies ahead of their face-to-face encounter with Mary.
The bubbly twins presented her with a bouquet of blooms.
Charlotte said her brush with royalty had left her friends in awe.
"We weren't supposed to tell anyone but we couldn't keep our mouths shut," she said.
Mary, who is mum to twins Prince Vincent and Princess Josephine, has been an international patron with the Australian Twin Registry (ATR) since January.
The registry, which pairs twins and research, has about 70,000 members, or 35,000 twins, with the oldest twin pair aged 97.
In a statement from the registry, Mary said she was proud to be the international patron for both the Australian Twin Registry and Danish Twin Registry.
"Twins are special as I now know as the mother of Vincent and Josephine," the statement read.
"What is perhaps less well-known is the special contribution twins of all ages have made to medical and health research though the Australian, Danish and other twin registries."
Mary and Frederik met the ATR director before they were introduced to twins and parents inside the hospital.
Mother Kristy Pereira said Frederik showed her twins, Kai and Siobhan, 5, photos of his children on his phone.
"(Kai and Siobhan) know they are boy and girl twins like Prince Frederik's as well so they were very excited," she told AAP.
Mary and Frederik left the hospital under a strong police presence, leaving awestricken princess-hopefuls and satisfied royalists in their wake.Mary and Frederik are in Sydney for the Opera House 40th anniversary.