The plot follows Mimiko (ミミ子), a bright little girl left alone when her grandmother leaves on a trip to her grandfather's memorial service in Nagasaki.

Making a few stops at some local stores, Mimiko comes home to her house in a bamboo grove and finds a baby panda named Panny (Pan-Chan) sleeping on the back doorstep.

Meanwhile, Mimiko and her family go out on a walk and, after scaring off some local bullies, they inadvertently lose Panny after he rolls down a hill.

They find Panny floating on a piece of wood, heading towards an open floodgate and hurry to save him.

PapaPanda, alongside Panny, return to work at the zoo, under the condition that they can leave after the visitors have left to spend time with Mimiko.

In a way similar to the story of Goldilocks, Panny finds what the ringmaster was looking for: a baby tiger named Tiny (Tora-chan).

To make matters worse, Panny crashes straight into the tiger cage, where Tiny's unhappy mother waits.

A frantic cry of help from Tiny (in the form of a makeshift bottled message) sends Mimiko and her family in a search for him.

Mimiko and her family go to free the animals, which they succeed in doing, but unintentionally cause the train to start (due to the playful antics of Panny and Tiny).

After extensive pre-production work, the trio travelled to Sweden to seek permission from Lindgren; their request was flatly refused.

Rejected, Takahata and Miyazaki joined Otsuka on the Lupin III Part I TV series as the "A-Pro directors team".

After Lupin's cancellation in 1972, the team revisited the Pippi Longstocking project, and reworked many of its ideas and story elements into the theatrical short film, Panda Kopanda.

Kondo would play a valuable role in many later Takahata and Miyazaki films, including Anne of Green Gables, Grave of the Fireflies, and Whisper of the Heart.

Miyazaki would pay tribute again in his films Laputa: Castle in the Sky, Porco Rosso and Yadosagashi (House Hunting).

Mimiko's handstands are referenced many times in Heidi, Girl of the Alps, 3000 Leagues in Search of Mother, and Future Boy Conan.

Papa Panda's enormous water splash into the lake is referenced in Lupin III: Castle of Cagliostro.

A pan shot of a crowd at the zoo includes cameos of Lupin and Jigen, as well as members of the production staff.