Baby pygmy hippopotamus Moo Deng and baby king penguin Pesto have recently taken the internet by storm. Photos and videos of their adorable antics have captured the hearts of the online public. With each racking up an impressive online following, some viewers have even pitted them up against each other as rivals. But who are they, and how did they come about? 

Moo Deng, whose name directly translates to “bouncy pork” in Thai, is a two-month-old hippo that lives in Khao Kheow Open Zoo in Thailand. Posts showing her biting her caretakers, mimicking her mother’s grass-chomping, and displaying frenzied expressions have flooded the internet since September of 2024 and have attracted upwards of 33 million views across social media platforms. As mentioned before, Moo Deng is a pygmy hippo, one of only two species hippopotamids in the world. The other, naturally, is the common hippo. The two have significant differences, especially in their size and behavior; pygmy hippos typically are solitary, whereas common hippos congregate in herds. Their most significant difference, however, is in their numbers. There are about 115,000 to 130,000 common hippos in the world while there are as few as an estimated 2,000 wild pygmy hippos remaining, making Moo Deng particularly special.

Beyond the pygmy hippo’s smaller population, the nocturnal species is very hard to see, as its habitat is found in the interior forests of West Africa. Most of them dwell in intact forests in Liberia, but some also live in Sierra Leone, Guinea and the Ivory Coast. Few scientists are able to study common hippos, and there are “even fewer who study pygmy hippos,” according to Rebecca Lewison, a conservation ecologist at San Diego State University. Unfortunately, logging and mining has put the pygmy hippo’s habitat in danger, thus increasing their rarity. 

Since pygmy hippos are so rare, it’s uncommon to witness the behavior of a pygmy hippo calf, so it's no wonder that Moo Deng has gained so much fame. Zoo visitors have doubled since her birth as crowds of fans flock to the zoo for a glimpse of her cuteness. 

The other rising internet superstar is Pesto, the baby king penguin based at the Sea Life Melbourne Aquarium in Australia. His posts have reached the eyes of nearly two billion people. Pesto has been on display at the aquarium since April of 2024, but what makes him so special is his unusual size. He just seems to never stop growing and weighs a whopping 51.8 pounds! Caretakers chalk up his unusual size to a “hearty appetite” of more than 25 fish a day as well as the penguin’s good genes. His biological father, a king penguin named Blake, is one of the biggest and oldest penguins at the facility, weighing in at around 39 pounds. However, according to the aquarium, Pesto is being raised by a younger couple–Tango and Hudson–who have been taking good care of him. For reference, the couple each weigh just about 24 pounds. As the aquarium’s education supervisor Jacinta Early puts it, Pesto “eclipses” the pair, “which also makes him look comically large.” Right now, Pesto is still covered in fuzzy brown down. But in the coming months, his baby feathers will be replaced by black, white and orange plumage. “He’s going to start losing that really adorable baby fluff,” says Early. “It might take him one to two months to really get rid of it. Then he’ll be nice and sleek and streamlined.” Around the same time, he may also lose some weight. As Pesto matures, he’ll likely settle in at closer to 33 pounds. 

Unlike pygmy hippos, according to the International Union for Conservation of Nature, king penguin numbers are increasing. They’re considered a species of “least concern.”

The remarkable popularity of adorable animals on social media is not new. So why are so many people drawn to animals? The cuteness factor has always been a big reason, but the internet’s latest favorites seem to have achieved a rare type of animal celebrity. A big part of that could be tied to each animal’s strong personality. Researchers have found that people are attracted to content and characters that validate their own experiences and reflect their own beliefs or feelings. “We do like to see characters that are going through the same thing we’re going through,” Matthew Grizzard, a communications professor at The Ohio State University, previously told the BBC.

When it comes to Moo Deng, her expression of apparent frustration–which commonly takes the form of open-mouthed yelling–embodies the stress and annoyance that many of her fans are experiencing amid ongoing uncertainty in the world. “I love that Moo Deng is so annoyed all the time. I can relate,” one online Moo Deng fan wrote. Pesto, in addition to his unique identity as a “chonky king,” has also become known for how much he enjoys food. His larger-than-average diet prompted internet observers to share their similar love of fish and sushi. “If you can assign this sort of unexpected emotion to an animal, it’s effective,” Roger Dooley, a consumer marketing expert, explained when asked about the deceased internet phenomenon, Grumpy Cat. “I think we don’t expect our animals to be grumpy, so as a result you have that novelty factor at work too.” Broadly, animal content has also been found to have a soothing effect on people that can help relieve stress by providing distraction or comfort. A 2019 University of Leeds Study, for example, found that showing college students preparing for finals a 30-minute montage of cute animal content helped reduce anxiety, blood pressure, and heart rates.

Like other viral animals that have come before them, Moo Deng’s and Pesto’s internet fame can be attributed to both their pleasing cuteness, and because they appear to convey emotions that reflect how many people are feeling at the moment.

Information retrieved form smithsonianmag.com and latimes.com