Weighing 22 kilograms (49 pounds) at 9 months old, Pesto is the heaviest penguin chick the Sea Life Melbourne Aquarium has ever had, its education supervisor Jacinta Early said on Friday.
By contrast, his doting parents, Hudson and Tango weigh 11 kilograms (24 pounds) each.
Pesto's global fame has grown with his size. More than 1.9 billion people around the world had viewed him through social media, an aquarium statement said.
He ate more than his own substantial body weight in fish in the past week: 24 kilograms (53 pounds), Early said.
The veterinary advice is that that quantity of food is healthy for a chick approaching adulthood.
His growth will plateau as he enters his fledging period. He has started to lose his brown feathers and will replace them with the black and white plumage of a young adult.
His keepers expect him to trim down to around 15 kilograms (33 pounds) in the process.
"He's going to start losing that really adorable baby fluff. It might take him one to two months to really get rid of it. Then he'll be nice and sleek and streamlined," Early said.
But she expects Pesto will remain recognizable as the sought-after TikTok celebrity he has become for another two weeks.
For now, he's a star attraction.
"Such a small head for such a big body," one admirer remarked on Friday as a crowd gathered against the glass of the penguin enclosure at feeding time.
Hatching on Jan. 31, Pesto was the only king penguin chick to hatch at the aquarium this year and the first since 2022, a year when there were six. The reason why there was none last year isn't clear.
Adult king penguins weigh between 9.5 kilograms (21 pounds) and 18 kilograms (40 pounds), according to the Antarctic and Southern Ocean Coalition, a global environmental group.
They are the world's econd largest penguin species, after the emperor penguin.