"Zannen na Ikimono Jiten" is a comedic and educational anime that explores the peculiarities and humorous shortcomings of various animals and creatures. The series is structured as a lighthearted encyclopedia, presenting each episode as a collection of short segments that focus on different species. Each segment humorously highlights the "regrettable" or seemingly inefficient traits of the featured creatures, often anthropomorphizing them to emphasize their quirks.

The narrative is driven by a narrator who provides factual information about the animals while injecting a comedic tone, often poking fun at their perceived flaws. The creatures are depicted in exaggerated, cartoonish ways, with their behaviors and characteristics amplified for comedic effect. For example, a segment might focus on a bird with an overly elaborate mating dance that ultimately fails to attract a mate, or a fish with a bizarre defense mechanism that backfires. The humor arises from the contrast between the animals' earnest efforts and their inevitable, often absurd, failures.

The main characters are the animals themselves, each given distinct personalities and traits that align with their real-world behaviors but are exaggerated for comedic purposes. The series does not follow a continuous plot but instead offers episodic, self-contained stories that revolve around the animals' daily lives, survival strategies, and interactions with their environments. Despite the comedic tone, the series subtly incorporates educational elements, providing viewers with factual insights into the biology and ecology of the featured species.

The animation style is simple and playful, complementing the lighthearted tone of the series. The pacing is brisk, with each segment lasting only a few minutes, making it accessible and easy to watch in short bursts. The humor is universal, relying on visual gags and situational comedy rather than dialogue-heavy jokes, which allows it to appeal to a broad audience, including younger viewers.

Overall, "Zannen na Ikimono Jiten" combines humor and education in a unique format, offering a fresh take on the natural world by celebrating the "regrettable" yet endearing traits of its animal protagonists. The series stands out for its ability to entertain while subtly imparting knowledge about the diversity and quirks of the animal kingdom.