Pesto the penguin towers over the colony at his Australian aquarium home, a fluffy brown furball impossible to miss as he waddles across the ice.

The nine-month-old king penguin chick has shot to fame for his 23.5-kilogram (51.8-pound) heft -- the weight of an overstuffed suitcase.

Pesto already weighs more than his parents Tango and Hudson combined. They tip the scales at about 11 kilograms each.

And with a healthy diet of up to 25 fish a day, Pesto's rotund frame will only continue to grow, senior penguin keeper Emily Thornton told AFP. 

The feathered unit is well-behaved, curious and confident, Thornton said, often interacting with other penguins and his keepers.

Despite the human faces and cameras pressed against Pesto's enclosure, he remains fairly "humble" about his newfound fame, she added.

And, because he is so "food orientated", just keeping him still on the scales to clock his weight can be challenging. 

He is already the largest penguin that the Sea Life Melbourne aquarium has seen and has a sizable social media fandom to match.

One TikTok video posted by the aquarium of two employees performing a dance routine behind an impassive Pesto has racked up four million views.

Hefty and healthy

Pesto's coat is mostly "dense" feathers, Thornton said, which penguin chicks require to keep warm against freezing Antarctic temperatures. 

His big size is also an advantage because smaller chicks are at risk of being eaten by predatory birds in the wild.

Genetics also play a part -- his ancestors were some of the biggest and oldest penguins the aquarium has housed.

"He is really healthy," Thornton said, adding that "chicks can get bigger than him" in the wild. 

Despite his fish diet, his feathers smell like corn chips, Thornton added.

Pesto will soon shed his fluffy down as he develops his adult feathers, giving him a burst of yellow on his head and cheeks and a black-and-white tuxedo.

"That process is energy draining and his appetite will reduce a lot," Thornton said.

King penguins are found in Antarctica and their population remains fairly stable, with about 1.6 million breeding pairs.

Thornton said climate change has badly affected the habitats of some penguin species but has not yet hit the king penguins' domain. 

During the 19th and 20th centuries, king penguin populations were almost wiped out because they were heavily hunted for their meat, oil and blubber.