The nine-month-old king penguin chick has shot to fame for his 23.5kg heft – the weight of an overstuffed suitcase.

Pesto already weighs more than his parents Tango and Hudson combined – and they tip the scales at about 11kg 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, 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 oriented”, 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.

Pesto’s coat is mostly “dense” feathers, Thornton noted, which penguin chicks require to keep warm against freezing Antarctic temperatures. His size is also an advantage as 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 hastened to add, saying “chicks can get bigger than him” in the wild.

Soon, Pesto will 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 pointed out.

King penguins are found in Antarctica and their population remains fairly stable, with about 1.6 million breeding pairs. According to Thornton, climate change has heavily impacted the habitats of some penguin species but has not yet impacted 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.