Penguin is an emperor penguin whose name is simply Penguin, a name that also serves as his legal name. He lives as an ordinary animal resident in a human community and is a regular customer of the café run by his friend Polar Bear, where his usual order is a café mocha. He is often seen wearing a scarf and has a rounded build typical of an emperor penguin.

His personality is generally calm, polite, and considerate, and he tends to read the mood of a conversation before joining in. He is described as delicate, serious-minded, and somewhat prone to worry, with a realistic way of thinking. Compared with the more free-spirited animals around him, he is the sensible one, and he frequently serves as the straight man, reacting with sharp retorts to Polar Bear's puns and to Panda's self-indulgent antics. Despite his composed surface, he has flaws: he sometimes tries to appear knowledgeable about subjects he does not actually understand, and he can be quick to blame outside factors for his own mistakes, such as when he blamed the driving instructor for failing his driving test. He is also somewhat absent-minded and meddlesome, and he has a notably low tolerance for alcohol, becoming talkative and sentimental when drunk.

Penguin's main motivation is to protect the stable, comfortable relationships and peaceful daily routines he values. He prefers the quiet continuation of ordinary days over sudden changes, and while unexpected events tend to fluster him, he ultimately acts in a way that prioritizes his friendships. He also carries a strong romantic streak, and a significant part of his personal storyline involves his pursuit of love, beginning with his crush on Penko, a lady penguin who works at a bakery.

In the story, Penguin functions as the common-sense anchor among the café's regulars. His bewildered reactions to the bizarre behavior of others create the rhythm of the comedy and give viewers a relatable perspective on the everyday scenes. He also acts as an emotional support within the group, listening seriously to his friends' problems and helping to keep the circle of companions stable.

His key relationships reflect this role. With Polar Bear, he has an easygoing friendship built on trust, and he willingly plays along with the puns even as he delivers the rebuttals. With Panda, he is a fellow regular who often gets dragged into Panda's lazy schemes; he is frequently swept along by Panda's carefree nature but still keeps a watchful, tolerant eye on him. With Grizzly, he shares a long acquaintance and remains a friend despite being taken aback by Grizzly's boisterous manner. He also interacts regularly with the café's human employee Sasako and with other frequent visitors such as Llama.

Penguin shows gradual development over the course of the series through recurring storylines rather than dramatic change. His romantic life is explored in several episodes, from his attempts to confess to Penko, to heartbreak, and later to a new interest. His everyday life is also given depth through episodes centered on his work as a sales penguin, his hobbies, his mishaps with driving, and even a personal secret revealed later in the series. Through these stories, he is portrayed as a realistic character with both strengths and weaknesses, but one who is consistently shown to be a genuine and dependable friend.

His notable abilities are mostly social and practical. He has a quick verbal wit that makes him an effective straight man, and he has a knack for calmly pointing out the absurdity in others' behavior. He is a good listener and a reliable source of emotional support for his friends, and his practical common sense helps ground the group's more eccentric decisions. He does not possess any special powers, and his ordinary limitations, such as his low alcohol tolerance and occasional clumsiness, are part of what makes him relatable.