Gender: Male First person: I (formal/authoritative) The leader of the secret unit, the Penguins. He acts as the tactical commander, naming operations and giving precise orders to his team. He is the second shortest of the four. He enjoys dark humor and has the personality of a stereotypical soldier. He can be a bit pushy. As Kowalski describes him as a "paranoiac," he is suspicious and occasionally makes wild deductions based on excessive delusions. However, once he falls for someone—even if it's an animal that is a natural enemy of penguins—he completely lets his guard down and loses sight of his surroundings; he is a man of many loves. He tends to look down slightly on non-birds and displays some old-fashioned behavior, but as a leader, he possesses high command and combat abilities (able to easily defeat his three subordinates alone). He is deeply loved by his team because he spares no effort to fulfill their wishes. He is a brave and bold egoist who will face alone what other team members tremble at. He has a habit of his eye twitching when he feels intense stress.

Gender: Male First person: I (formal/polite) The brains of the Penguins, responsible for situation reports and devising plans. He is the tallest of the four. He carries a clipboard and pen, instantly analyzing the situation. He sometimes uses an abacus or scales. While confident in his intelligence, he is poor at reading human writing, so his plans and reports consist mostly of drawings. When his brain or body is damaged, he may make very childish remarks. He usually speaks calmly, but his voice cracks when he gets excited. He is a science fanatic who gets abnormally excited about it, sometimes losing sight of his surroundings and putting his comrades in danger; in short, he is a calm mad scientist. He believes the power of science is absolute and is an atheist who rejects magic and superstitions. He seems frustrated that Skipper and the others don't understand chemistry.

Gender: Male First person: Rico The most violent and physical penguin of the group. He is the second tallest. The feathers on the back of his head stand up, and he has a scar on the left side of his beak. He rarely speaks actual words compared to the others, communicating through grunts, roars, single words, or onomatopoeia, which is often hard for non-members to understand. When responding, he says "Yah" for "Yeah." His catchphrases are "Kaboom!" and "Fish!" Rarely, he might speak a full phrase like "Dunno." He can store weapons and tools in his bottomless stomach, vomiting up hammers, dynamite, or paperclips for picking locks upon request. Skipper calls him a "world-class eccentric." He loves explosives like bombs and bazookas and wants to destroy everything. It's also his job to destroy Kowalski's failed inventions. When he goes out of control due to rage, he turns into a weapon of destruction himself, becoming unstoppable. Skipper generally views this craziness as an asset and gives orders to utilize it in appropriate places; Rico is highly loyal to Skipper and follows him well. Utilizing his ability to take things in and out, he can function like a shredder, machine gun, or vacuum cleaner. He is a glutton, especially for fish and candy. He also has a side that is abnormally prone to believing superstitions and cherishes his girlfriend, Perky (a doll modeled after a blonde girl), which contrasts with his usual ferocity.

Gender: Male First person: I (soft/polite) The youngest member and the most sensible penguin. He is the shortest of the four, though almost the same height as Skipper. His head is rounder than Skipper's, and his overall body shape is round like a Matryoshka doll. He has a very gentle and kind personality, and his selling point is his cuteness. Despite this, his combat skills are high, such as dodging Skipper's attacks while blindfolded. He can be well-spoken, but due to his immaturity, he sometimes accidentally leaks base secrets to other animals. Though timid, he sometimes performs physically demanding missions, and undercover work is his specialty. He often ends his sentences with a polite "sir" or "-ssu" equivalent. He has a habit of shouting "Chest!" when taking action. He loves fairy tales and is a huge fan of an animated show featuring colorful unicorns. He believes in magic. He lacks the ruthlessness of a soldier and is sometimes scolded by Skipper for trusting animals who are clearly villains or for trying to find non-violent solutions. On the other hand, the team feels his purity should be protected; it's a tradition for the other penguins to cover Private's eyes or ears when faced with something extreme or inappropriate.