The story follows Calimero, a small anthropomorphic black chick who is the only one of his color in a family of yellow chickens. He is instantly recognizable by the half eggshell he wears permanently on his head, a visual remnant of his hatching. The character originally appeared in a series of Italian television commercials for a soap product before being adapted into a full animated series through a collaboration between Italian creators and Japanese animation studios.

The central conflict of the series stems from Calimero's frequent perception of being treated unfairly because of his small size and misfortunes, often leading him to exclaim his iconic catchphrase, It is an injustice. Despite his tendency to complain, he is a well-intentioned and charming character who embarks on various adventures with his group of friends. The setting is a vibrant, whimsical world populated by other young animal characters, where everyday situations often escalate into unexpected problems that the group must solve together.

The main cast includes Priscilla, a sensible yellow chick who is Calimeros girlfriend. The group also includes Piero (also known as Peter or Pierrot), a duck who initially acts as a rival and troublemaker but later becomes a friend in subsequent series. Other recurring characters are Valeriano (or Giuliano), a green chick obsessed with filmmaking, and Susy, a wealthy duck.

The narrative structure of the anime differs across its three major productions. The first Japanese anime series, produced by Toei Animation in 1974, consists of 47 episodes and focuses on the groups many adventures as they solve mysteries and make documentaries, which frequently lands them in trouble. A second series produced in 1992 introduces a new setting and an expanded cast, where Calimero takes on a more proactive, heroic role as the leader of his friends. A third series, produced in 2013 using computer animation, relocates Calimero and his core friends to the town of Belladagio (or Hatchington). In this version, their adventures center around an old mill that contains a secret laboratory filled with inventions from Calimeros great-great-grandfather, Do Vinci, which serves as the hub for their explorations.